Slice 3: executor, agent-browser adapter, store, and tyto run

[rvegajr]

Stacked on #6. Spec sentences are in docs/IMPLEMENTATION.md §4 Slice 3, updated in this PR to match what was built. Hand-written recipes now replay with no model.

What

Core

• executeRecipe: lint → render → one agent-browser batch → verify.
• Exit codes: 0 hit, 3 miss, 64 bad params, 65 invalid recipe, 69 agent-browser missing, 70 internal, 75 session busy, 77 not approved.
• Replay-session policy:
  • tyto-rx runs with Tyto's own agent-browser config via AGENT_BROWSER_CONFIG. agent-browser's source (flags.rs load_config) confirms that config replaces the user's entirely, so saved logins never load. It also runs with --allowed-domains.
  • tyto-rx-auth uses --restore main and runs only approved auth recipes.
• Retry once, only on browser launch errors. 15 s overall deadline. 6 s action timeout.
• New ports: BrowserRunner, RecipeStore, SessionLock, with fakes.
• Recipes gain domains: CDN hosts the page may load from, added to the allowlist.

@tyto/agent-browser

• Spawns the CLI with an argv array, never a shell string.
• Sends batch steps as JSON on stdin and strips lifecycle noise.
• Reports step failures without throwing; kills the child on abort.
• Typed errors when the binary is missing or the output is unreadable.

@tyto/store

• Recipe files are validated on save and load, written 0600 and atomically, and only kebab-case names are accepted.
• O_EXCL session lock that reclaims locks whose holder process has died.
• ensureReplayFiles writes the replay config (only executablePath copied from your config) and the policy {default: allow, deny: [download, upload]}.

@tyto/cli

• tyto run, tyto test (regression cases), tyto recipes [--json | show | rm].
• bin/tyto.mjs runs the TypeScript sources directly. New packages use erasableSyntaxOnly so that stays possible.

Tests

• npm run check: 8 files, 73 tests, typecheck clean, gitleaks clean.

• The adapter tests use a stand-in executable, so there's no browser or network.

• npm run test:live (opt-in, real agent-browser, loopback page): 2 passed. A recipe hits, then misses after the page changes; a missing element fails in under 7 s.

• Manual end to end, with a hand-written GitHub recipe, through the user's Edge:

  Case	Result
  vercel-labs/agent-browser	v0.38.1 ✅
  nodejs/node	v26.10.0 ✅ (an older LTS release is listed first; the recipe follows the Latest badge)
  denoland/deno	v2.9.7 ✅
  Missing repo	Safe miss, exit 3
  --n two	Exit 64
  tyto test	1/1 passed

  Runs took 1.4–2.1 s each, including a live GitHub page load.

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