feat(web): keyboard shortcuts cheat sheet (?) + a11y audit (keyboard nav, ARIA, contrast)

[subinium]

Severity: priority/warning
Source: Internal UX audit (v0.7 sweep)
Area: packages/web

Problem

• No keyboard shortcuts cheat sheet (Cmd+K palette would be exposed via ? standard).
• Most interactive elements aren't keyboard-navigable. Screen-reader semantics are missing on custom Lit components.
• Color contrast not audited — some text on the dark theme may fail WCAG AA.

Proposed fix

1. ? opens a modal listing all shortcuts (palette opener, persona switch, theme toggle, reload, focus-composer, scroll-to-latest, etc.).
2. Keyboard nav: every interactive element reachable via Tab. Custom <crowclaw-*> components implement focus() + arrow-key handling where appropriate (e.g., session list).
3. ARIA: every custom button has role="button" + accessible label. Modals trap focus + escape-closes.
4. Contrast: run axe-core in a CI check; fix all AA failures.
5. Screen reader: visible focus rings + skip-to-main link.

Expected impact

• Compliance with corp accessibility requirements (often blocks enterprise sales).
• Power-user productivity uplift (no-mouse workflow).

References

• Internal v0.7 platform polish audit

[subinium]

Verifier-confirmed shipped via v0.7.x / v0.8.0 / v0.8.1 / v0.8.2 sweeps. The earlier release PR descriptions used range syntax (#230–#240, #241–#250) which does not trigger GitHub auto-close, leaving these in OPEN state despite the implementation landing. v0.8.3 verifier pass confirmed code presence and acceptance criteria via grep and file inspection on main (commit 72fa31b). If acceptance criteria are not actually met for this specific issue, please reopen with the missing detail and it will be picked up in the next sweep.