feat: expose official OMP capabilities in clients

[wolfiesch]

What this changes

T4 now uses the operation capabilities reported by official OMP as the source of truth for slash-command presentation in both client families.

• web/Electron and Flutter show discovered headless commands as selectable
• terminal-only commands stay visible but disabled with the runtime-provided reason
• typed catalog commands such as session.cancel are not mistaken for slash commands
• Flutter slash search includes runtime-provided aliases
• older hosts without operation capabilities retain the legacy catalog fallback
• the 104-row OMP coverage tracker and audit are updated for the official-OMP adapter architecture and current merged PRs

Verification

• pnpm --filter @t4-code/client test — 255 passed
• pnpm --filter @t4-code/web test — 1,196 passed
• client and web TypeScript checks passed
• pnpm lint passed
• pnpm check:release passed
• pnpm check:provenance passed
• tracker CSV validation passed

Flutter controller and widget tests are included. The local machine does not have the Flutter SDK, so Flutter analysis/tests are delegated to required CI.

Proof boundary

This exposes runtime truth; it does not add typed plan, goal, branch/fork/tree, provider-auth, or child-agent operations. Those remain explicit gaps in the tracker.

[chatgpt-codex-connector]

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