fix(ui): restore shimmer for running trow summaries

[Astro-Han]

Summary

Restore the shared TextShimmer treatment for active trow summary text while keeping completed trow summaries stable.

Why

Issue #882 tracks the follow-up from PR #874: grouped trow summaries expose running state, but the summary text was still rendered as plain text. This makes active tool-group changes feel abrupt and leaves the existing shimmer contract unused.

Related Issue

Fixes #882

Human Review Status

Approved by @Astro-Han

Review Focus

Please check that the shimmer is scoped only to active trow summary text and that completed summaries do not keep an active animation node.

Risk Notes

The change adds one shared TextShimmer instance to active trow summaries, so the main risk is render/perf cost during tool-heavy sessions. Targeted snap and perf probe scenarios passed. Platform/packaging checklist item is unticked because this touches only web-rendered UI component code and snap coverage.

How To Verify

RED check: bun run snap session-trow failed before implementation because active running-current trow had no active TextShimmer node.
bun install --frozen-lockfile: installed dependencies in the isolated worktree.
bun run typecheck: passed.
bun test --preload ./happydom.ts ./src/components/session-turn-trow-block.reducer.test.ts: 19 passed.
bun run snap session-trow: passed; screenshot grid generated at docs/design/preview/screenshots/session-trow.png.
PAWWORK_PERF_SCENARIOS=tool-call-expand bun run test:e2e:local:perf: 1 passed, 9 skipped.
PAWWORK_PERF_PROFILE=low-end PAWWORK_PERF_SCENARIOS=concurrent-shimmer-extreme bun run test:e2e:local:perf: 1 passed, 9 skipped.
git diff --cached --check: passed.
Review follow-up for Gemini suggestion: removed keyed remount path for TextShimmer text updates.
Follow-up bun run typecheck: passed.
Follow-up bun test --preload ./happydom.ts ./src/components/session-turn-trow-block.reducer.test.ts: 19 passed.
Follow-up bun run snap session-trow: passed.
Follow-up git diff --check: passed.

Screenshots or Recordings

Updated snap target: session-trow, generated docs/design/preview/screenshots/session-trow.png.

Manual Electron check passed by @Astro-Han.

Checklist

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Summary by CodeRabbit

Release Notes

• New Features

  • Added shimmer loading animations to session summary text during active operations and various summary states

• Tests

  • Extended snapshot tests to verify shimmer animation visibility and behavior across different session summary display states

[coderabbitai]

📝 Walkthrough

Walkthrough

Session-turn-trow-block now wraps active summary text with the TextShimmer component. The CSS documentation describes the shimmer behavior, and e2e snapshot tests validate that running trows display active shimmer while collapsed states remain still.

Changes

Trow Summary Shimmer

Layer / File(s)	Summary
TextShimmer component integration packages/ui/src/components/session-turn-trow-block.tsx, packages/ui/src/components/session-turn-trow-block.css	TextShimmer is imported and wrapped around the summary text in the single-row details/summary path with active={!!activeTool()}. CSS documentation is updated to describe the shimmer behavior and reduced-motion handling, replacing the prior caller-wired shimmer model.
E2E shimmer state assertions packages/app/e2e/snap/session-trow.snap.ts	ACTIVE_SHIMMER selector constant is added and assertions are extended to validate that running-current shows an active shimmer while both collapsed states (activity-summary-collapsed and failed-summary-collapsed) show zero active shimmers.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Suggested labels

bug

Poem

🐰 A shimmer dance for tools in flight,
Active summaries now glow just right—
Subtle motion, respectful and lean,
The shimmer returns to the trow scene!
✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: restoring shimmer UI treatment for active (running) trow summary text, which aligns with the PR's primary objective.
Linked Issues check	✅ Passed	The PR fully addresses #882 objectives: TextShimmer is applied to active trow summaries via updated session-turn-trow-block.tsx [in raw_summary], completed summaries remain stable, reduced-motion is respected, snapshot coverage was added, and perf probes passed.
Out of Scope Changes check	✅ Passed	All changes are in-scope: three files modified (snapshot test assertions, CSS documentation, and TSX component logic) directly implement the shimmer restoration without altering grouping model, summary copy, or unrelated surfaces.
Description check	✅ Passed	The pull request description is comprehensive and follows the required template with all major sections completed, including summary, context, issue link, human review status, review focus, risk notes, verification steps, and a fully-ticked checklist.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/i882-trow-summary-shimmer

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[github-actions]

Suggested priority: P2 (includes non-doc, non-test paths outside the low-risk bucket).

P1/P0 are reserved for maintainer confirmation. Please relabel manually if this is a release blocker, security issue, data-loss risk, or updater/runtime failure.

[gemini-code-assist]

Code Review

This pull request integrates the TextShimmer component into the TrowBlock to handle loading states for summary text and updates the end-to-end tests to verify the shimmer's visibility. A review comment identifies that using the keyed attribute on the <Show> component causes unnecessary remounting, which triggers unwanted entry animations and breaks the internal transition logic of TextShimmer. It is recommended to remove the keyed attribute and treat the text as an accessor to ensure smoother visual transitions.

[github-actions]

Perf delta summary

Comparator: pass

Profile / Scenario	interaction median	interaction worst	long task max	tbt	frame gap p95	frame gap max	jank count	cls	status
default / tool-default-open-heavy-bash	16 -> 16 (0)	16 -> 16 (0)	77 -> 66 (-11)	41 -> 16 (-25)	50 -> 50 (0)	133.3 -> 116.6 (-16.7)	3 -> 3 (0)	0.004 -> 0.004 (0)	pass