feat(agent): add Antigravity (agy) as a first-class agent

[Rfluid]

Implements docs/plans/antigravity-agent.md, included in the branch.

Google's Antigravity CLI (agy) is a fourth agent in daily use with its own rate-limit windows that nothing else surfaces. This puts them in the tray ring, the Quota tab, the Forecast tab and aura quota, and adds an activity-only reader.

Three commits, reviewable in order:

766f82e	fix(reader) — deterministic peak_hour. Independent pre-existing bug.
c02141f	refactor(core) — share executable lookup between plugins and agents. No behaviour change for plugins.
bdec11c	feat(agent) — the agent itself.

Quota — why a subprocess

agy -p "/usage" --output-format json. A direct call to the underlying RPC was investigated and rejected: agy keeps its OAuth token in the OS keyring, and v1internal:retrieveUserQuotaSummary is gated on the CLI's own client identity — a valid bearer token alone returns 403 You do not have a valid license of this product. Going direct would mean a reverse-engineered internal proto, a license handshake, and cross-platform keyring credential handling, all undocumented.

The slash command is answered locally from a cached backend reading, so it starts no LLM turn and consumes no quota (num_turns: 0). A 20s TTL cache absorbs the ~3s of Go-binary startup. Windows are reordered so position 0 is the session and position 1 the week, matching every other agent and keeping the tray_*_source defaults meaningful.

Activity — conversation_summaries.db

Read via diesel (bundled SQLite). Opened read-only through file:…?mode=ro so a running agy is never blocked — deliberately not immutable=1, which reads the main file alone and would silently miss anything still in the WAL; that's the fallback for when -shm can't be created.

Rows from both the CLI and the Antigravity IDE count. They share one account and one table (app_data_dir distinguishes them); filtering to CLI-only reduced a real profile from 13 sessions spanning 278 days to 1.

No token counts

Antigravity's trajectories are schema-less protobuf with no plaintext model names, so there is nothing to attribute. AgentKind::reports_tokens answers this synchronously and UsageSnapshot::tokens_unreported carries it on a loaded snapshot; a test pins the two together. The Models tab is dropped entirely rather than rendered blank — both its chart and its per-model bars are token-derived. The selected section is resolved against the visible list at render time, so switching profiles while sitting on Models falls back to Quota instead of desyncing.

Also in here

• New optional command key on agent profiles, for an install outside PATH.
• bin_path. Aura runs from a GUI launcher, a systemd user unit or a launchd agent, none of which source shell rc files — so PATH omits ~/.local/bin, which is exactly where agy installs itself. The plugin runner already compensated when spawning children; that logic is now shared, and binaries are resolved to an absolute path up front. That matters for portability: Unix resolves a bare program name against the PATH handed to the child, but Windows resolves it against the parent's.
• aura quota's WINDOW column 14 → 18. Claude/GPT · week is the first 17-character label any backend has produced.

Cross-platform

Verified by reading the sources that decide the behaviour, not by running on those machines:

• SQLite URI — checked against sqlite3ParseUri. In the filename state it treats exactly %, ?, # specially, so & and = are literal and must not be encoded. No drive-letter special case, so file:C:/dir/x.db is correct. The authority check runs on the raw string before decoding, so a UNC path would fail with invalid uri authority; the second slash is encoded to sidestep it.
• Windows console — aura is windows_subsystem = "windows", so a console-subsystem child opens a window. agy is one and the tray polls every 30s; CREATE_NO_WINDOW prevents a CMD window flashing twice a minute.
• Windows binary location — agy installs to %LOCALAPPDATA%\agy\bin, which is searched explicitly.
• macOS — launchd gives a bundled app only /usr/bin:/bin:/usr/sbin:/sbin, and agy's installer adds its directory to your shell profile, which launchd never reads. Covered by the same fallback list. The bundle uses the hardened runtime with no entitlements file, so it is not sandboxed and spawning is unrestricted.
• Data dir — ~/.gemini/antigravity-cli on all three; agy hardcodes that relative path.
• Compilation — the #[cfg]-gated code type-checks on all six release targets.

aarch64-pc-windows-msvc is the one target that cross-compiles rather than building natively, which now matters because bundled SQLite compiles C. The runner image carries Microsoft.VisualStudio.Component.VC.Tools.ARM64, and that target is already experimental: true.

Testing

302 tests pass (+58), clippy --all-targets -D warnings clean, fmt clean.

Verified against a live agy 1.2.4 install: setup-config detection, aura quota returning all four windows with reset times, aura usage reporting 13 sessions / 1673 messages over 278 days (and 1 session / 2 messages at --period 7d), and the whole thing working under the real systemd user-unit PATH. The icon renders to a clean arc through usvg/resvg 0.45, the same pipeline gpui::SvgRenderer uses.

Not verified by execution: the modal's rendering of the hidden Models tab, and anything on Windows or macOS. Worth a look from a launched (not terminal) Aura if you have either.