emrg: GUI file browser — chevron indicators + tree scroll fix

[argszero]

Summary

Implements host rant 2026-08-13T20:58:57 — two file-browser issues:

1. Missing expand/collapse chevron on directory rows (VS Code-style ▸/▾).
2. File tree cannot scroll vertically.

Changes

• file-tree.js: add chevronRight/ chevronDown to ICON; iconSvg(d, cls) gains an optional class param; chevronFor(entry) maps expanded state → chevron path; directory rows (and the root row) prepend a .ft-chevron before the folder icon; toggleDir syncs the chevron innerHTML on expand/collapse. File rows get no chevron.
• layout.css: add flex-shrink: 0 to .ft-row — .ft-row is a flex item of .result-files (flex column) with overflow:hidden, so its min-height:auto resolves to 0 and the whole tree compresses to container height (scrollHeight == clientHeight, never scrolling). flex-shrink: 0 prevents the compression. Add .ft-chevron style.
• renderer.smoke.test.js: add P3.5 test asserting root chevron = ▾ (M3 6l5 5 5-5z), collapsed dir chevron = ▸ (M6 3l5 5-5 5z), expands to ▾ on click, and file rows have no chevron.
• Agent.md: GUI test count 237 → 238 (renderer smoke 115 → 116).

Verification

• node --check on touched JS: OK
• cd emrg/gui && npm test: 238/238 pass
• uv run pytest tests/ -q: 801 passed
• uv run python -c "from emrg.client.app import run_client" + uv run python -m emrg --help: OK

[argszero]

✅ LGTM — cycle (1/3)

Full-diff review (actual PR diff = merge-base..head, 4 files):

• file-tree.js: chevronRight/chevronDown ICONs (correct VS Code ▸/▾ paths), iconSvg(d, cls) optional class param (backward-compatible), chevronFor() maps expanded state, dir rows + root row prepend .ft-chevron, toggleDir syncs chevron innerHTML on expand/collapse; file rows get no chevron. Clean.
• layout.css: .ft-chevron (flex:none, 14px, margin-right 2px, fill currentColor) + the key fix — .ft-row { flex-shrink: 0 }. Verified the cascade: .result-files is a flex column (via .result-pane.active) with overflow-y:auto; .ft-row items default flex-shrink:1 + overflow:hidden → min-height:auto resolves to 0 → whole tree compresses → scrollHeight==clientHeight, never scrolls. flex-shrink:0 prevents the compression. Correct root cause + fix (matches the #733-era .result-files min-height:0 scrollbar intent).
• renderer.smoke.test.js: +1 P3.5 test — root chevron ▾ (M3 6l5 5 5-5z), collapsed dir ▸ (M6 3l5 5-5 5z), click → ▾, file rows no chevron. Discriminates the chevron behavior in both states.
• Agent.md: GUI 237→238 (renderer smoke 115→116) synced.

Note: branch base is pre-#768 (3dbd600) — the reversal lines only appear when diffing against new master; GitHub's squash diff (merge-base..head) is exactly these 4 files, so merge applies cleanly. CI test-windows PASS (test pending). Approving.

[argszero]

✅ LGTM — cycle (2/3)

Fresh re-verification this cycle (head f37ecc9 unchanged since first review):

• file-tree.js: chevronRight/chevronDown ICONs (correct VS Code ▸/▾ paths), iconSvg(d, cls) keeps backward compat, chevronFor() reads the same expanded Map that drives dirOpen/dirClosed — chevron state can never desync from folder state; toggleDir syncs both icons on expand/collapse; file rows get no chevron; root row (default expanded) prepends ▾.
• layout.css: .ft-chevron (flex:none + 14px + fill currentColor) + flex-shrink: 0 on .ft-row — correct root cause: .result-files flex column + overflow-y:auto, .ft-row shrink:1 + overflow:hidden collapses min-height to 0, tree compresses to container height so scrollHeight==clientHeight. Fix restores the intended scroll.
• renderer.smoke.test.js: +1 test covers root ▾ / collapsed ▸ / click→▾ / files no-chevron.
• Agent.md GUI count 237→238 synced.

Checks: test + test-windows PASS. mergeable: CLEAN. Approving.

[argszero]

✅ LGTM — cycle (2/3)

Full-diff review of the feature code (f37ecc9, unchanged in cf32eb6):

• file-tree.js: chevronRight/chevronDown icons + chevronFor(); dir rows prepend chevron in .ft-head; toggleDir syncs both the dir icon and chevron; root row defaults to ▾ (chevronDown) with click binding (#733) preserved.
• layout.css: .ft-row { flex-shrink: 0 } — fixes the scroll-compression root cause (flex column item with overflow:hidden collapses to container height → scrollHeight==clientHeight); .ft-chevron sizing/margin.
• renderer.smoke.test.js: P3.5 test covers root ▾, collapsed dir ▸, click → ▾, and file rows have no chevron (positive+negative).

cf32eb6 = doc reconciliation: Agent.md GUI count bumped 238→239 (117 renderer smoke) since #768 merged first (both PRs add 1 renderer smoke test); merged master will truly have 239. Verified: pytest 801, GUI 238/238 on branch, node --check, import + CLI OK, CI test + test-windows PASS.

[argszero]

✅ LGTM — cycle (3/3)

Head advanced f37ecc9 → 954dc9a (author doc-sync cf32eb6: Agent.md 238→239 / renderer smoke 116→117 to account for #768's merged regression test — verified the count math: master's #768 test + this PR's +1 chevron test = 239/117, correct; I then merged master in to clear the Agent.md same-line conflict — resolution kept 239/117, verified the merged-tree diff vs master is exactly the intended 4-file delta: Agent.md + layout.css + file-tree.js + renderer.smoke.test.js).

Fresh re-verification of the resolved head (code content unchanged since the 2/3 review):

• file-tree.js: chevronRight/chevronDown ICONs, iconSvg(d, cls) backward-compatible, chevronFor() reads the same expanded Map as dirOpen/dirClosed (desync-proof), toggleDir syncs both icons, root row ▾ default, file rows no chevron.
• layout.css: .ft-chevron (flex:none 14px) + .ft-row flex-shrink:0 — root cause confirmed against the cascade (.result-files flex column + overflow-y:auto, .ft-row shrink:1+overflow:hidden → min-height:auto 0 → tree compressed → scrollHeight==clientHeight).
• renderer.smoke.test.js: +1 chevron test (root ▾ / collapsed ▸ / click → ▾ / files no-chevron).
• Agent.md 239 sync (both doc sites).

CI run 31704433911 test + test-windows PASS on 954dc9a. mergeable: MERGEABLE/CLEAN. Approving.