mouse-override icon: document in layout spec, switch glyph to CursorTextIcon

[dormouse-bot]

What

Two related changes to the mouse-reporting override indicator in the pane header.

1. Document the override icon in the layout spec. The pane-header section of docs/specs/layout.md omitted the mouse-reporting override icon entirely — it was absent from both the "Elements from left to right" list and the responsive-tier breakdown. The icon has lived in the header for a while (defined in docs/specs/mouse-and-clipboard.md), but #148 made its tier behavior concrete: it now drops at the minimal tier (showMouseIcon && tier !== 'minimal' in TerminalPaneHeader.tsx). That change updated the code without updating layout.md, leaving the placement/tier spec — which AGENTS.md designates as the source of truth for header element placement and sizing — incomplete.

2. Switch the override glyph to CursorTextIcon. While the override is active, the No-Mouse indicator previously rendered Phosphor's SelectionSlashIcon; it now renders CursorTextIcon. This is a user-visible runtime change to the glyph shown when an override is in effect. The mouse-and-clipboard.md and layout.md specs are updated to match.

Changes

Docs (docs/specs/layout.md, docs/specs/mouse-and-clipboard.md):

• Add the mouse-reporting override icon to the header element list, in its actual position (after the flexible gap, before the split icons).
• Cross-reference docs/specs/mouse-and-clipboard.md for its visual states/behavior, mirroring how the bell and TODO pill point at alert.md.
• Update the three tier descriptions: the icon is visible in the full and compact tiers and hidden in minimal, and it only appears at all when the inside program requests mouse reporting.
• Update the No-Mouse icon's Phosphor name from SelectionSlashIcon to CursorTextIcon.

Runtime (lib/src/components/wall/TerminalPaneHeader.tsx):

• Replace SelectionSlashIcon with CursorTextIcon for the override indicator (import + render site).

Verification

Cross-checked against the source: the render order in lib/src/components/wall/TerminalPaneHeader.tsx places the icon between the flexible (flex-1 overflow-hidden) region and the tier === 'full' split/zoom block, gated on tier !== 'minimal'; tier thresholds (>280 full, >160 compact, else minimal) match the ResizeObserver callback. Terminology (CursorClickIcon / CursorTextIcon, "Mouse icon") matches mouse-and-clipboard.md. Build & Test is green.

The icon swap has no automated test; it's a single-glyph substitution with no behavioral branch beyond the existing inOverride conditional.

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View logs

[dormouse-bot]

The docs additions check out: I traced the render order in TerminalPaneHeader.tsx and the override-icon block (showMouseIcon && tier !== 'minimal') sits after the flexible-gap region and before the tier === 'full' split block — matching the new element-list position and the per-tier visibility now spelled out in layout.md. The SelectionSlashIcon → CursorTextIcon swap is consistent: no SelectionSlashIcon references remain anywhere, CursorTextIcon is already imported/used in MobileTerminalUi.tsx, and Build & Test is green.

One scope observation: the second commit (refactor(mouse): use CursorTextIcon…, 38704ca) changes the glyph users actually see when an override is active — a user-visible runtime change — but the PR title (docs(layout):) and the body ("Changes (docs only)" / "documentation-only change with no runtime behavior") predate it and now describe only the first commit. On a squash-merge that would file the icon change under docs. Worth refreshing the title/body to cover the icon refactor so the merged history reflects both concerns.

[dormouse-bot]

Addressed the scope observation from the review: refreshed the PR title and description so they cover the CursorTextIcon glyph swap (a user-visible runtime change) alongside the layout-spec docs, rather than describing only the first commit as "docs only". The merged history will now reflect both concerns.