v0.9.14: App-server typed command catalog for client slash-command surfaces

[Hmbown]

Why this matters

GPUI Hmbown/codewhale-apps#556 (Linear APPS-28) requires the composer to route slash commands through shared command definitions — "the existing Codewhale command registry, aliases, hidden tiers and user-command shadowing," with host commands like /settings or /compact never submitted as paid model prompts. Without a served catalog, the desktop must hardcode a second command list that rots against the registry.

Current behavior

• The command registry, aliases, hidden tiers and user-command shadowing live TUI-side; there is no /v1/commands (or equivalent) route — the full /v1/* route table in crates/tui/src/runtime_api.rs contains no command surface.
• Clients cannot distinguish "Engine-handled host command" from "model prompt" without duplicating the registry.
• Command contract: finish the FEAT-02x adoption or fold crates/command-contract #6145 covers the internal crates/command-contract adoption question; this issue is the client-facing read surface regardless of where the registry lands.

Desired behavior

1. A route serving the typed command catalog: name, aliases, summary, hidden/tier flag, argument shape, and whether it is host-handled vs model-bound — enough for a client to complete, validate, and never submit a host command as a prompt.
2. User-command shadowing reflected in the served result (a user command that shadows a builtin must win).
3. Forward-compatible: unknown command kinds must be ignorable by older clients.

Acceptance criteria

• GET on the route returns the full catalog including aliases and hidden-tier markers
• A user-defined command shadowing a builtin appears with the winning definition
• Each entry states host-handled vs model-bound so a client can gate submit
• cargo test -p codewhale-tui route test covers catalog shape and shadowing

Related: Hmbown/codewhale-apps#556, #6145 (command-contract adoption), #6152.

[Hmbown]

Landed in 70cda6e43 + d5291dfb66.

• GET /v1/commands serves the typed catalog: name, aliases, localized summary, usage, parsed literal subcommands, takes_arguments, hidden/discovery tier, kind (builtin/user, forward-compatible), binding (host/prompt), shadowed_by/shadowed_aliases for user-command shadowing.
• Shadowing verified over HTTP: a workspace .codewhale/commands/model.md makes the builtin model report shadowed_by: "model" while the winning user row serves with binding: "prompt".
• Catalog is derived from the existing command registry + user registry — no second command list to rot.

Tests: cargo test -p codewhale-tui --lib --locked command_catalog — 3 passed, 0 failed, including get_v1_commands_serves_the_catalog_over_http (route-level shape + shadowing).