feat: add AGY (Antigravity) harness adapter, interactive prompts, and slash commands

[Kryvonis]

Summary

Adds support for AGY (Google Antigravity CLI / agy / antigravity) to Collie:

1. Interactive Prompt Up-Leveling (web/src/lib/harness/agy/):

   • Lifts ask_question dialogs, numbered options (1. Option, 1) Option, [1] Option, ( ) 1.Option), and permission/confirmation prompts into native tappable buttons.
   • Handles options with or without explicit footer hint lines.
   • Guards against free-text sends while an interactive prompt is open (composerReady).
   • Re-derives signatures through the race guard before sending keystrokes ([digit, "Enter"] or [digit]).

2. Slash Command Palette (web/src/lib/agent-commands.ts):

   • Adds the public AGY command catalog with prefix matching for agy, agy-cli, and antigravity:
     /plan, /grill-me, /learn, /compact, /clear, /model, /status, /subagents, /skills, /rules, /mcp, /hooks, /review, /diff, /doctor, /theme, /help, /exit.

3. Brand Styling & Icon (web/src/components/agent-icon*):

   • Adds the official brand mark and tile background (#1A73E8) for agy and antigravity pane badges and switcher tiles.

4. Registry & Case/Prefix Normalization (web/src/lib/harness/registry.ts):

   • Normalizes agent keys in adapterFor to support casing and common prefix variants (agy, agy-cli, antigravity).

   ---

Suggested CHANGELOG Entry

AGY (Antigravity CLI) gets a harness adapter — up-levels interactive question options (ask_question) and tool permission dialogs into tappable buttons, gates the composer against typing into active menus, adds the AGY slash command palette, and includes brand icons.

Verification

- **Harness Unit Tests:**
  `cd web && bunx vitest run src/lib/harness/agy/` (7 passed)
- **Commands & Icon Tests:**
  `cd web && bunx vitest run src/lib/agent-commands.test.ts src/components/agent-icon.test.tsx` (39 passed)
- **Full Frontend Suite:**
  `cd web && bun run test` (108 test files, 2,161 tests passing)
- **Bridge Tests:**
  `bun test bridge/` (559 tests passing)
- **Typecheck & Production Build:**
  `cd web && bun run typecheck && bun run build` (0 errors, clean build)
- **Live Local Test:**
  Verified prompt button tapping and submission against a live `agy` session on Herdr.

[AltanS]

Thanks — the agy work is welcome. The command catalog and the icon are fine as they are.

The adapter emits prompt-select, whose keystroke recipe is already live, so this is Tier 2 in HARNESS_CONTRIBUTING.md and needs: a captured fixture corpus, a notes file with the verified recipe, a describeAdapterConformance call, and live verification. I can't do the last one — agy isn't installed here.

Two changes I'd want regardless:

1. keys: [n, "Enter"] synthesises digits from numbered rows, and the detector matches any numbered list near the tail — it'll claim /model and /skills. ADR 0009 closes that off (in Claude's /model a digit also rewrites the user's default). Drive it from the footer, or record the live probe showing agy's digits are safe.

2. Please drop the adapterFor prefix-matching — it widens claude/omp to any agent string with those prefixes. Separate PR, separate argument. Register agy by its exact agent strings.

Bring the corpus + notes + conformance and run the live check on your session, and I'll take it whole.

[AltanS]

Both asks are addressed — adapterFor is exact-keyed again, and the detector is footer-gated so /model and /skills stay raw. Thanks. Three things before I take it.

1. The fixtures aren't captures. Every file in the corpus is a byte-faithful format:ansi capture with real ESC bytes; the 8 agy files have none, and their rule widths disagree between files (60 vs 113 columns).

claude--select-menu.txt  27 ESC     grok--ask-color.txt   54 ESC
codex--ask-fruit.txt     78 ESC     agy--select-menu.txt   0 ESC

This is the one that blocks the rest: the keystroke table in AGY_NOTES.md is the only evidence the recipe is right, and hand-typed screens can't corroborate it. Capture them with scripts/capture-fixture.sh <paneId> <name> off a sandbox agy pane. If you need to scrub a username or path, keep the substitution length-preserving so the row padding stays byte-identical — see the codex corpus note in the fixtures README.

2. chrome.ts never finds the input box. ? for shortcuts matches its PROMPT_REGEX (the \?\s* branch), so the walk stops on the status line. On your own fixtures:

agy--fresh-idle.txt  DRAFT = "for shortcuts    accept-edits · Gemini 3.7 Flash · low"
agy--done.txt        DRAFT = "for shortcuts    accept-edits · Gemini 3.7 Flash · low"
agy--fresh-idle.txt  blocks = [{raw, 9 lines}]      // the box is still in the mirror

Collie would paint that as the operator's draft. extractStatusLines returns [] unconditionally too, so the status row is never lifted out. Please cover both against a fixture — the unit tests use hand-built strings, which is why this got through.

3. Please restore the completeness gate in prompt-binding-contract.test.ts. Narrowing it to claude-- also switches it off for codex, grok and omp. With the original filter, five agy fixtures come back unpinned:

agy--permission-bash, agy--permission-edit, agy--plan-approval,
agy--select-menu, agy--trust-prompt

Claude's detectPromptSelect claims all five. Add their regions to prompt-binding-regions.json rather than shrinking the filter.

Two notes, not conditions. isAlienBuffer is carrying more weight than it looks: with that one function stubbed out, the agy grammar claims 12 foreign fixtures with digit keys. Nothing routes that way in production, so it isn't a live hazard — but it tells you the grammar is loose, and a real agy screen that prints Enter to select will be claimed the same way. A brand-name blocklist won't catch that one. Separately, the gemini → someunknown edit in agent-icon.test.tsx looks unrelated; gemini is still an unknown agent everywhere else.

Bring the real captures and the chrome fix and I'll take it.