Port /impeccable generate to the engine crates

The Node-era server, CLI, hook, and pin halves of the generate command move
into the Rust workspace, with the protocol unchanged:

- crates/live: POST /agent-target is held open on a channel plus a timer
  thread (the manual-apply deferred pattern), releasing its turnstile
  ticket before it parks like /poll; /agent-target-result resolves it;
  /agent-target-claim is the roll call with its renewable lease. SSE
  connections carry the overlay's clientId: a late overlay is replayed
  every pending target, and a disconnect retires that overlay's report,
  releases its lease, and re-judges each roll call. Shutdown drains held
  requests with server_stopping.
- crates/live/src/live_generate.rs: the live-generate verb (the router
  already forwards every live* verb), same flags, verdicts, and
  _instructions, spelled with the engine's self command.
- crates/hook: every entry stands down on live preview markers
  (skipped: live-preview), checking the proposed content and the file on
  disk for hook-before-edit.
- crates/context: pin accepts generate; the crate's command-metadata.json
  copy carries its entry.

Tests: crates/cli/tests/agent_target.rs (six HTTP cases with an SSE reader),
tests/live-agent-target.test.mjs rewritten to drive the binary (28 cases,
registered in the live suite), hook stand-down cases, oracle goldens for
live-generate plus the re-recorded pin list goldens, the e2e prompt
assertion waiting for the journaled event, and the contract documented in
docs/CLI-CONTRACT.md.

AI-assisted: implemented and tested with Claude Code under maintainer
direction.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates/context/src/command-metadata.json

@@ -19,6 +19,10 @@
     "description": "Interactive live variant mode. Select elements in the browser, pick a design action, and get AI-generated HTML+CSS variants hot-swapped via HMR. Requires a running dev server. Use when you want to visually experiment with design alternatives in real time.",
     "argumentHint": ""
   },
+  "generate": {
+    "description": "Agent-driven live variant generation. Boots live mode, finds the named element on the open page, scrolls the browser to it, and delivers N variants in the requested direction for the user to cycle and accept. Use for requests that name an element and a direction, like 'generate 3 bold variants of the pricing cards', skipping manual element picking.",
+    "argumentHint": "[count] [direction] variants of [element]"
+  },
   "adapt": {
     "description": "Adapt designs to work across different screen sizes, devices, contexts, or platforms. Implements breakpoints, fluid layouts, and touch targets. Use when the user mentions responsive design, mobile layouts, breakpoints, viewport adaptation, or cross-device compatibility.",
     "argumentHint": "[target] [context (mobile, tablet, print...)]"

crates/context/src/pin.rs

@@ -13,10 +13,10 @@ const HARNESS_DIRS: [&str; 18] = [
     ".pi", ".opencode", ".kiro", ".rovodev", ".vibe", ".qoder",
 ];
 const CODEX_HARNESSES: [&str; 2] = [".codex", ".agents"];
-pub const VALID_COMMANDS: [&str; 23] = [
+pub const VALID_COMMANDS: [&str; 24] = [
     "craft", "init", "extract", "document", "shape", "critique", "audit", "polish", "bolder", "quieter", "distill",
     "harden", "onboard", "live", "animate", "colorize", "typeset", "layout", "delight", "overdrive", "clarify",
-    "adapt", "optimize",
+    "adapt", "optimize", "generate",
 ];
 const PIN_MARKER: &str = "<!-- impeccable-pinned-skill -->";
 const OPENCODE_PIN_MARKER: &str = "<!-- impeccable-pinned-command -->";