fix(client): put the settings footer links in the AccessKit tree (UI/UX v3 P4d)

[mizu-jun]

The defect

Measuring for #96 turned this up: accessibility.rs did not mention settings-open-config-file or settings-reset-category anywhere. The settings panel's two footer actions — open config.toml, reset the current category — were reachable by mouse and by nothing else. A screen-reader user could not perform either.

It was kept out of #96 deliberately: that PR was typography and hit-region geometry, and this is a P6c-shaped accessibility gap.

The fix

Both links become Role::Button nodes — SETTINGS_FOOTER_OPEN_ID (31) and SETTINGS_FOOTER_RESET_ID (32), taken from the id block the hand-written settings fields vacated in P1b/P1c — and children of the panel dialog beside the content group, which is where they sit on screen.

Button rather than Link: both perform an action rather than navigate, and "Open config.toml" hands off to the OS editor.

Three things the fix pins:

• The label is the link's text without its glyph. footer::open_text() / reset_text() are the bare localised strings, and the drawn labels are format!("↗ {}", open_text()) — so a reworded link cannot say one thing on screen and another out loud. ↗ / ↺ are a visual affordance; reading them aloud before every activation is noise.
• The reset node exists only while category_resettable(). The renderer omits the link for the list-based categories (SSH / Keybindings / Profiles), where a reset would delete user data; announcing a control that is not drawn would be a worse defect than the omission being fixed. The tree hash already covers the transition — it hashes category.label(), and resettability is a function of the category.
• Click performs the same two actions the mouse arm does (platform::open_config_file() / reset_category_to_defaults() + redraw), guarded on the panel being open so a stale activation cannot open an editor or reset a category behind the user's back.

Also corrects the node-id range table, which still described 28..30 as "reserved" after P6c took them for the InfoBar slots.

Verification

• cargo fmt --check — clean
• cargo clippy --workspace --all-targets -- -D warnings — no warnings
• cargo test --workspace — 28 suites pass; 3 new tests (both links present as panel children with a Click action; no reset node for any of the three non-resettable categories; labels equal footer::open_text() / reset_text() and carry no glyph) plus decode round-trips for the two new ids
• Not covered: a real screen-reader pass. The tree is asserted, not heard.

Stacked on #96 (merged); the diff here is P4d only.

🤖 Generated with Claude Code

[github-actions]

Coverage report

Generated by cargo llvm-cov (workspace minus nexterm-client-gpu and nexterm-i18n).