Add file identity icons and animated transcript tool activity

[gaelcado]

Summary

• Bundle the MIT-licensed Symbols file-icon theme and render its full-color file and folder identities throughout the UI: workspace tree and search, file preview, composer mentions, change rows, right-pane file tabs, transcript file actions, and standalone Markdown file references.
• Resolve exact names, longest compound extensions, language and MIME hints, then generic fallbacks. Preserve authored icon artwork while lifting selected dark-theme accents and placing icons on subtle appearance-aware wells where surrounding chrome needs contrast.
• Turn live transcript tool groups into a compact activity tree. Headers, rows, connectors, branch tips, and tool glyphs reveal in sequence; active summaries shimmer, detail disclosures animate independently, and interrupted folds continue from their visible height. Full tool history remains in the normal transcript scroll area.
• Respect reduced-motion settings and retain existing detail state while a tool group changes or completes.

Validation

• cargo test -p zeron-ui --lib --quiet: 896 passed.
• rustfmt --edition 2024 --check crates/ui/src/transcript.rs and git diff --check: passed.
• cargo fmt -p zeron-ui -- --check still reports existing unrelated formatting drift in UI examples, browser, and terminal files.
• No application preview or screenshot capture was launched for this review.

Compatibility and attribution

Symbols artwork and its filename/folder associations are pinned to 296ef1b62287fb2315cb5651e552e09e8c8e1de8; its MIT license and notice are included in the bundled assets and THIRD_PARTY_NOTICES.md. Icons are decorative alongside their text labels. No engine, protocol, data migration, or settings changes.

[avarayr]

imo the tree segment lines from the left are animated nicely, but it adds a bit too much clutter to the minimal aesthetic.

[gaelcado]

CI investigation for head c578194:

• The failed iOS job has one failure among 107 tests: TranscriptLayoutTests.testToolGroupsRevealAndCollapseThroughIntermediateHeights measured 24 pt of gap variation against a <4 threshold.
• The complete apps/ios tree and CI workflow are identical to the passing main run and passing composer run. Logs also show the same Xcode 26.6 and resolved Swift package versions. This job builds the iOS project, not the changed desktop Rust UI.
• The test took 15.763 s in the failed run versus approximately 4 s in both passing runs. This suggests investigating scheduling sensitivity, but does not establish the cause.

The evidence strongly suggests this PR did not introduce the iOS failure. It does not distinguish a sampling/timing issue from a real intermittent iOS animation/layout defect: the assertion measures presentation-layer geometry.

Suggested next step: inspect the retained tool-opening-motion / tool-closing-motion attachments, then repeat on the same commit if appropriate. No CI reruns or assertion changes were made during this investigation. Is this a known intermittent issue, and would you prefer a same-commit rerun or a separate tracking issue?

[wingleeio]

No blocking findings. Reviewed icon resolution/assets, Markdown decoration, and tool activity/fold lifecycle. The full UI suite passes locally: 923 tests on the PR head and 923 after integrating current main (2704615). Changed-file formatting passes apart from pre-existing formatting reached through child modules; diff checks pass. The original iOS failure is unrelated to this desktop change: apps/ios has the identical Git tree 5124e4f6d1a05b32e8892ca4aa168b109ddea229 in this PR, main, and #341, where the same testToolGroupsRevealAndCollapseThroughIntermediateHeights test passes (job 103807982096). All original desktop, browser, sync, and networking checks pass. The failed iOS job has also been rerun.