<!-- markdownlint-disable MD041 -->

Adds a progress visualization system for the `ocm transfer component-version` command, providing real-time feedback during long-running transfers.

**Terminal mode** (interactive TTY):
- Animated spinner during resolve phase
- Progress bar with scrolling item log during transfer execution
- Color-coded status icons (✓/✗/⊘) and error formatting with spec dumps

**Non-terminal mode** (piped output, CI):
- Structured slog output for each operation phase and item-level events
- Automatically selected by the tracker when stderr is not a TTY

**Architecture:**
- `progress` package: orchestrates operation lifecycle via `Tracker`, `Simple`, and `Tracked` factories. Owns the slog-based default visualizer for non-terminal mode.
- `visualizers` package: terminal-specific rendering implementations (`basicVisualizer` for spinners, `barVisualizer` for progress bars). Decoupled from domain types.
- Transfer command's `progress.go`: adapter layer mapping graph runtime events to progress events, with domain-specific error formatting.

**Key design decisions:**
- Tracker stores output writer and terminal flag; factory functions (`VisualizerFactory`, `EventVisualizerFactory`) receive these from the tracker, keeping the caller API minimal: `progress.Simple(visualizers.Simple)` and `progress.Tracked(visualizers.NewBarVisualizer(formatError), total, events, mapper)`
- slog is intercepted and buffered during terminal rendering to prevent log output from corrupting the animated UI; buffered lines are drained between render frames
- `SyncBuffer` provides thread-safe access to the shared log buffer between slog writers and visualizer render loops
- Transfer command refactored: cobra handler delegates to `transferRunner` which separates resolve/build/execute phases from rendering concerns

<!--
Usage: `Fixes #<issue number>`, or `Fixes (paste link of issue)`.
-->

Fixes: open-component-model#929

Signed-off-by: Piotr Janik <piotr.janik@sap.com>

<!-- markdownlint-disable MD041 -->

Adds a progress rendering system for the `transfer component-version` command, replacing the previous generic tracker with a streamlined, operation-based API.

**Progress package (`cli/internal/render/progress/`)**
- `Tracker[T]` manages operation lifecycle and slog redirection during terminal rendering
- `StartOperation` supports simple operations (spinner only) and event-tracked operations (progress bar) via `WithEvents` and `WithErrorFormatter`
- `SlogVisualizer[T]` provides automatic fallback for non-terminal environments (CI, piped output)
- slog is buffered during terminal rendering to prevent log output from corrupting the animated UI

**Bar visualizer (`cli/internal/render/progress/bar/`)**
- Single `NewVisualizer[T]` factory handles both simple (total=0, spinner header) and tracked (progress bar with scrolling item log) modes
- Animated spinner with shimmer effect on header text
- Failed items are listed with typed error formatting (spec dump for debugging)

**Transfer command integration**
- Three progress phases: loading transfer spec, resolving component versions, transferring
- Events are fully typed as `Event[*graphPkg.Transformation]` throughout the pipeline
- Error formatter renders transformation failures with error tree and framed spec JSON dump

<!--
Usage: `Fixes #<issue number>`, or `Fixes (paste link of issue)`.
-->

Fixes: open-component-model#929

Signed-off-by: Piotr Janik <piotr.janik@sap.com>

<!-- markdownlint-disable MD041 -->

Adds a progress rendering system for the `transfer component-version` command, replacing the previous generic tracker with a streamlined, operation-based API.

**Progress package (`cli/internal/render/progress/`)**
- `Tracker[T]` manages operation lifecycle and slog redirection during terminal rendering
- `StartOperation` supports simple operations (spinner only) and event-tracked operations (progress bar) via `WithEvents` and `WithErrorFormatter`
- `SlogVisualizer[T]` provides automatic fallback for non-terminal environments (CI, piped output)
- slog is buffered during terminal rendering to prevent log output from corrupting the animated UI

**Bar visualizer (`cli/internal/render/progress/bar/`)**
- Single `NewVisualizer[T]` factory handles both simple (total=0, spinner header) and tracked (progress bar with scrolling item log) modes
- Animated spinner with shimmer effect on header text
- Failed items are listed with typed error formatting (spec dump for debugging)

**Transfer command integration**
- Three progress phases: loading transfer spec, resolving component versions, transferring
- Events are fully typed as `Event[*graphPkg.Transformation]` throughout the pipeline
- Error formatter renders transformation failures with error tree and framed spec JSON dump

<!--
Usage: `Fixes #<issue number>`, or `Fixes (paste link of issue)`.
-->

Fixes: open-component-model#929

Signed-off-by: Piotr Janik <piotr.janik@sap.com>

<!-- markdownlint-disable MD041 -->

Adds a progress rendering system for the `transfer component-version` command, replacing the previous generic tracker with a streamlined, operation-based API.

**Progress package (`cli/internal/render/progress/`)**
- `Tracker[T]` manages operation lifecycle and slog redirection during terminal rendering
- `StartOperation` supports simple operations (spinner only) and event-tracked operations (progress bar) via `WithEvents` and `WithErrorFormatter`
- `SlogVisualizer[T]` provides automatic fallback for non-terminal environments (CI, piped output)
- slog is buffered during terminal rendering to prevent log output from corrupting the animated UI

**Bar visualizer (`cli/internal/render/progress/bar/`)**
- Single `NewVisualizer[T]` factory handles both simple (total=0, spinner header) and tracked (progress bar with scrolling item log) modes
- Animated spinner with shimmer effect on header text
- Failed items are listed with typed error formatting (spec dump for debugging)

**Transfer command integration**
- Three progress phases: loading transfer spec, resolving component versions, transferring
- Events are fully typed as `Event[*graphPkg.Transformation]` throughout the pipeline
- Error formatter renders transformation failures with error tree and framed spec JSON dump

<!--
Usage: `Fixes #<issue number>`, or `Fixes (paste link of issue)`.
-->

Fixes: open-component-model#929

Signed-off-by: Piotr Janik <piotr.janik@sap.com>

<!-- markdownlint-disable MD041 -->

Adds a progress visualization system for the `ocm transfer component-version` command, providing real-time feedback during long-running transfers.

**Terminal mode** (interactive TTY):
- Animated spinner during resolve phase
- Progress bar with scrolling item log during transfer execution
- Color-coded status icons (✓/✗/⊘) and error formatting with spec dumps

**Non-terminal mode** (piped output, CI):
- Structured slog output for each operation phase and item-level events
- Automatically selected by the tracker when stderr is not a TTY

**Architecture:**
- `progress` package: orchestrates operation lifecycle via `Tracker`, `Simple`, and `Tracked` factories. Owns the slog-based default visualizer for non-terminal mode.
- `visualizers` package: terminal-specific rendering implementations (`basicVisualizer` for spinners, `barVisualizer` for progress bars). Decoupled from domain types.
- Transfer command's `progress.go`: adapter layer mapping graph runtime events to progress events, with domain-specific error formatting.

**Key design decisions:**
- Tracker stores output writer and terminal flag; factory functions (`VisualizerFactory`, `EventVisualizerFactory`) receive these from the tracker, keeping the caller API minimal: `progress.Simple(visualizers.Simple)` and `progress.Tracked(visualizers.NewBarVisualizer(formatError), total, events, mapper)`
- slog is intercepted and buffered during terminal rendering to prevent log output from corrupting the animated UI; buffered lines are drained between render frames
- `SyncBuffer` provides thread-safe access to the shared log buffer between slog writers and visualizer render loops
- Transfer command refactored: cobra handler delegates to `transferRunner` which separates resolve/build/execute phases from rendering concerns

<!--
Usage: `Fixes #<issue number>`, or `Fixes (paste link of issue)`.
-->

Fixes: open-component-model#929

Signed-off-by: Piotr Janik <piotr.janik@sap.com>

<!-- markdownlint-disable MD041 -->

Adds a progress rendering system for the `transfer component-version` command, replacing the previous generic tracker with a streamlined, operation-based API.

**Progress package (`cli/internal/render/progress/`)**
- `Tracker[T]` manages operation lifecycle and slog redirection during terminal rendering
- `StartOperation` supports simple operations (spinner only) and event-tracked operations (progress bar) via `WithEvents` and `WithErrorFormatter`
- `SlogVisualizer[T]` provides automatic fallback for non-terminal environments (CI, piped output)
- slog is buffered during terminal rendering to prevent log output from corrupting the animated UI

**Bar visualizer (`cli/internal/render/progress/bar/`)**
- Single `NewVisualizer[T]` factory handles both simple (total=0, spinner header) and tracked (progress bar with scrolling item log) modes
- Animated spinner with shimmer effect on header text
- Failed items are listed with typed error formatting (spec dump for debugging)

**Transfer command integration**
- Three progress phases: loading transfer spec, resolving component versions, transferring
- Events are fully typed as `Event[*graphPkg.Transformation]` throughout the pipeline
- Error formatter renders transformation failures with error tree and framed spec JSON dump

<!--
Usage: `Fixes #<issue number>`, or `Fixes (paste link of issue)`.
-->

Fixes: open-component-model#929

Signed-off-by: Piotr Janik <piotr.janik@sap.com>

<!-- markdownlint-disable MD041 -->

Adds a progress rendering system for the `transfer component-version` command, replacing the previous generic tracker with a streamlined, operation-based API.

**Progress package (`cli/internal/render/progress/`)**
- `Tracker[T]` manages operation lifecycle and slog redirection during terminal rendering
- `StartOperation` supports simple operations (spinner only) and event-tracked operations (progress bar) via `WithEvents` and `WithErrorFormatter`
- `SlogVisualizer[T]` provides automatic fallback for non-terminal environments (CI, piped output)
- slog is buffered during terminal rendering to prevent log output from corrupting the animated UI

**Bar visualizer (`cli/internal/render/progress/bar/`)**
- Single `NewVisualizer[T]` factory handles both simple (total=0, spinner header) and tracked (progress bar with scrolling item log) modes
- Animated spinner with shimmer effect on header text
- Failed items are listed with typed error formatting (spec dump for debugging)

**Transfer command integration**
- Three progress phases: loading transfer spec, resolving component versions, transferring
- Events are fully typed as `Event[*graphPkg.Transformation]` throughout the pipeline
- Error formatter renders transformation failures with error tree and framed spec JSON dump

<!--
Usage: `Fixes #<issue number>`, or `Fixes (paste link of issue)`.
-->

Fixes: open-component-model#929

Signed-off-by: Piotr Janik <piotr.janik@sap.com>