Summary

• Adds browser-style project/global topic tabs so separate projects and topics can run concurrently.
• Replaces the flat session-focused sidebar with a project workspace tree and topic management.
• Adds a right-side workspace dock for files, changed files, and topic context, with chat-centered split-pane behavior.
• Refines per-message actions for forking, summarizing, and rolling back conversation/code from a chosen user turn.
• Adds persisted desktop preferences for language, appearance, close behavior, tab modes, and workspace layout.

What This PR Does

Project/topic workspace model

• Introduces workspace tabs with project/global scopes, topic ids, topic titles, active-tab delegation, tab ordering, and persisted restore.
• Routes controller events by tab id so background tabs keep streaming output, tool state, approvals, asks, jobs, cost, balance, and transcript state while another tab is active.
• Stores tab mode (normal, plan, yolo) per tab and restores it with the tab metadata instead of treating mode as one global composer state.
• Normalizes Wails-bound arrays before they reach React so empty Go slices render as [] rather than null.

Sidebar, tab bar, and dock layout

• Reworks the left project tree and top tab strip into a browser-like workspace shell with compact active states, stable row alignment, and yolo mode badges.
• Makes the right dock a real split pane owned by the web layout, not by native-window resizing side effects.
• Keeps the right-side toggle responsible only for collapsing/expanding the right dock; it no longer collapses the left sidebar or changes the native window size.
• Moves the 文件 / 改动 controls to the left side of the right dock header and makes them responsive as the dock is dragged narrower.
• Uses the requested first-open layout as the default when no user layout preference exists: left sidebar about 17.5% of the window, right file tree about 25%, and the chat pane gets the remaining centered space.
• Persists manual sidebar and right-dock widths after the user drags them, so the default ratio applies only before the first manual layout change.
• Splits right-dock width preferences by mode: file-tree width is compact by default, while preview mode can expand independently.

Message actions and rollback UX

• Replaces the old message menu wording with the clearer action set:
  • 分叉会话
  • 总结这条之后
  • 总结这条之前
  • 仅回滚对话
  • 仅回滚代码
  • 回滚代码和对话
• Removes the redundant 从这条消息开始 label.
• Adds checkpoint metadata for whether a turn can roll back conversation and/or code, and disables impossible menu actions with a concrete reason.
• Adds confirmation states for destructive rollback actions and surfaces changed-file counts where code rollback is available.
• Wires the desktop frontend through tab-aware checkpoint and message-action controller calls so the action applies to the selected tab, not an arbitrary active controller.

Desktop preferences and native shell behavior

• Moves desktop UI language and theme persistence from frontend-only localStorage into desktop config, with one-time migration from older localStorage values.
• Adds a General settings section for language and close behavior.
• Adds a close behavior preference: close-to-background or quit.
• Adds native single-instance behavior so launching the app again restores/shows the existing desktop window instead of creating an ambiguous second instance.
• Adds a native menu quit path that can bypass close-to-background when the user explicitly quits.

Config and CLI support

• Extends config edit/migration/render paths to include desktop preferences without mixing them into CLI prompt language semantics.
• Keeps CLI language behavior separate from desktop UI language.
• Updates boot/config/control tests around the new config fields, tab modes, and message action state.

Root Cause

• The desktop app was centered on one active controller/session, so switching workspaces replaced the active conversation instead of preserving multiple project-specific conversations.
• Background tab events needed durable routing by tab identity; dropping non-active events caused streaming output, tool state, approvals, asks, and rollback checkpoints to disappear when users switched tabs.
• The right-side workspace area had overlapping ownership between native window size, chat width, and dock width, which caused the right dock toggle to produce unrelated layout changes such as sidebar collapse or clipped controls.
• Layout defaults were fixed pixel values, so first-open proportions did not match the intended left/chat/right balance on common desktop widths.
• Wails-bound Go slices can serialize as null, which made React list rendering brittle when project/topic/context arrays were empty or absent.

Technical Approach

• Introduced workspace tab management with per-tab controllers, tab metadata, persistence, active-tab delegation, and tabId event routing.
• Added workspace-root-aware boot/config loading so project tabs scope config, skills, memory, hooks, commands, codegraph, and LSP state without changing process cwd.
• Extended session metadata with scope, workspace root, topic id, topic title, and tab mode so topics can be restored and resumed.
• Reworked frontend controller state into a per-tab state map and added TabBar, ProjectTree, ContextPanel, right-dock layout preferences, and shared Wails array normalization.
• Collapsed right-dock sizing into a deterministic grid allocator: left sidebar width, chat width, and dock width are separate state concepts, and the dock width is clamped against the available chat budget.
• Added rightDockTreeWidth and rightDockPreviewWidth layout preferences so compact file browsing and wider previewing do not fight each other.
• Added checkpoint capability metadata plus tab-aware message-action APIs for fork/summarize/rollback operations.
• Added desktop config fields and migration helpers for appearance, language, and close behavior.
• Added Wails SingleInstanceLock, close interception, and explicit quit handling for native desktop lifecycle behavior.

Focused Optimization Points

• Preserves background tab streaming, tool, approval, ask, transcript, and mode state while only switching the active view.
• Restores persisted tab ids and resumes the latest session for each topic id.
• Ensures Wails-bound array responses encode as [] instead of null, with regression coverage.
• Aligns the left project tree, top tab strip, and right workspace dock with the expected browser-like workspace layout.
• Keeps the chat pane as the visual center and prevents the right dock from causing horizontal overflow at common desktop widths.
• Keeps file-tree-only right dock compact on first open while allowing preview mode to expand when needed.
• Neutralizes the light theme surfaces away from the previous warm beige tone for a cleaner product workspace presentation.
• Keeps desktop UI language separate from CLI/model language so changing the desktop interface does not rebuild or perturb model prompt behavior.

Verification

• npm run build in desktop/frontend
• go test ./... in desktop
• go test ./internal/boot ./internal/config ./internal/control ./internal/cli ./internal/fileref ./internal/agent
• git diff --check
• git diff --cached --check
• Playwright/Chrome DOM audit for first-open layout after clearing reasonix.layoutPreferences.v1:
  • 2048px window: sidebar 358px, chat 1170px, right dock 512px, horizontal overflow 0
  • 1920px window: sidebar 336px, chat 1096px, right dock 480px, horizontal overflow 0
  • 1600px window: sidebar 280px, chat 912px, right dock 400px, horizontal overflow 0
  • 1280px window: sidebar 228px, chat 760px, right dock 284px, horizontal overflow 0
• Playwright/Chrome persistence audit with saved layout preferences:
  • saved sidebarWidth=300 and rightDockTreeWidth=420 remain 300/420 after refresh, proving user manual layout overrides the first-open default