Goal

Strengthen W1 regression coverage so that more of the session-view rewrite is blocked by CI before human retest, and the remaining manual pass is reserved for true visual judgment.

When this task is complete, the missing W1 regression coverage is tracked in one place across behavior assertions, computed-style assertions, checklist segmentation, and correct tool-failure test guidance.

Scope

In scope:

• Add the remaining W1 behavior assertions that are still being checked manually.
• Add low-cost computed-style assertions where screenshot diff is unnecessary.
• Split the local W1 checklist into CI-covered vs human-visual sections.
• Document correct stderr-producing commands for tool-failure tests.

Detailed scope:

A. Behavior assertions

Add E2E specs for scenarios currently relied on by manual handtest:

• scroll: reading_history persistence across content_resize / dock_resize
• scroll: weak trackpad gesture (multiple low-delta wheels) still demotes to reading_history
• scroll: nested raw tool output gesture isolation from parent timeline
• chevron: 12px size + collapsed-right / expanded-down orientation
• thinking indicator: only renders when working && assistantVisible === 0; disappears once any reasoning / prose / tool appears
• bubble selectability: user-select: text on user-message-text / bubble-text / agent-prose / agent-reasoning subtrees

B. Computed style assertions

Add computed-style assertions for:

• user bubble hairline: dark --border-weak, light --border-weaker inset box-shadow
• trow-result-body inner descendants: mono-small font + fg-weak color, with no sans/base/large leakage
• collapsible chevron icon size: 12px (DESIGN.md L412)

C. Handtest checklist segmentation

Update docs/design/session-view-w1-manual-checklist.md to split into two sections:

• CI must pass first — items already covered by smoke gate
• 5-minute visual pass — items that still require human design judgment

D. Tool failure test command guidance

Document that false is not a valid stderr-display test command because it produces no output by design. Recommend:

• ls /definitely-not-exist
• node -e 'console.error("boom"); process.exit(1)'

Out of scope:

• Electron E2E
• visual-diff infrastructure (Percy / Chromatic / Playwright snapshots)
• Tool Display Spec Registry (tracked separately in [Feature] Agentic trow summary for tool calls #596)

Relevant files or context

Background:

• Per task [Feature] Polish right panel tabs (Terminal, Review, Status) #71 research, the W1 manual handtest is too expensive because CI does not yet gate enough renderer and interaction behavior.
• PR refactor(session): rewrite session view per W1 visual lock for slice 11b.1 #589 already delivers smoke-gate inclusion as the first step; this issue tracks the remaining coverage work.
• Tool summary follow-up is tracked separately in [Feature] Agentic trow summary for tool calls #596.

Likely files:

• packages/app/e2e/session/session-w1-*.spec.ts
• packages/app/e2e/session/session-renderer-diagnostics.spec.ts
• local checklist: docs/design/session-view-w1-manual-checklist.md

Verification

• New behavior and computed-style specs pass within the current smoke runtime budget.
• Checklist is split into CI-covered vs human-visual sections.
• Failure-command guidance is updated in the checklist.
• New specs pass on a clean main without regressing existing smoke coverage.

Execution mode

Agent should investigate and propose a plan first