feat(web): anchor the composer settings sheet to the clicked value button

[KorenKrita]

Problem

Since #1475 the composer shows [model] and [effort] value buttons whose captions are the current values. Clicking either one opened the same full settings sheet as the gear, always rendered from the top in the fixed order Model → Effort → Permission → other. So clicking Effort never took you to Effort — you landed on the Model section and had to scroll past every model row to reach the control you asked for. The label on the button promised a specific destination the sheet did not deliver.

Changes

HappyComposer gains a settingsSection state ('model' | 'effort' | null) that anchors the open sheet:

• model button expands only the Model area (including the Cursor variant drill-down).
• effort button expands only the Effort / Reasoning-effort area.
• gear keeps the full sheet (null anchor).
• Clicking the other value button while the sheet is open switches sections in place rather than closing, so model → effort is one click.
• Clicking the gear over an anchored sheet expands it to the full sheet.
• Re-clicking the same trigger still closes, preserving the feat(web): composer model/effort value buttons and first-class permission (part of #1438) #1475 toggle-close behaviour.

Implementation notes:

• The section gating happens on sheet-local flags derived inside the overlays memo (sheetModelSettings, sheetEffortSettings, …), so the section-divider conditions keep working and a single visible area never renders a leading, trailing, or orphaned divider.
• handleGearToggle is a zero-arg wrapper for the DOM onClick consumer, so a MouseEvent can never leak into the section parameter.
• modelValueOpen / effortValueOpen now highlight only while their own area is expanded, instead of both lighting up whenever the sheet was open.
• dismissSettings clears the anchor along with the sheet and the Cursor drill-down, so no stale anchor can survive a dismissal.

Unchanged: the outside-click dismissal exemption for all three triggers, Pi's mid-turn control liveness (configurationControlsDisabled, #1442), the Cursor variant drill-down flow, and narrow-viewport behaviour (value buttons hidden, gear opens the full sheet).

Testing

• web: 2558 tests pass, bunx tsc --noEmit clean.
• Updated HappyComposer.modelEffortButtons coverage: anchored open from each value button (asserting the other sections stay collapsed), in-place section switching, gear opening the full sheet, and the gear expanding an already-anchored sheet.

[github-actions]

Findings

• None.

Questions

• None.

Summary

• Review mode: initial. No reportable issues found in the latest full diff. Residual coverage risk: the added tests do not exercise effort → model, full-sheet → anchored transitions, or Cursor drill-down followed by gear expansion.

Testing

• Not run (automation). At review time, the GitHub integration check passed; test and pr-review were pending.

HAPI Bot