Recall UserPromptSubmit hook hangs (2s timeout) when embed-daemon.js launcher is missing from embed-deps despite embeddings enabled

## Symptom

Every prompt in Claude Code fails with:

```
UserPromptSubmit hook timed out after 2s — output discarded. Raise the hook's "timeout" to allow more time.
```

It is **persistent across fresh sessions** and unaffected by anything in the user's `settings.json` (the offending hook lives in the plugin's own `hooks.json`). Net effect: proactive recall is **never** injected — it always times out and is discarded.

## Environment

- hivemind `0.7.116` (Claude Code plugin)
- Node `v25.8.1`, macOS `15.6.1` (arm64)
- `~/.deeplake/config.json` → `{ "embeddings": { "enabled": true } }`
- Embed deps installed: `~/.hivemind/embed-deps/node_modules` present (508 MB, `@huggingface/transformers`)

## Root cause

The embedding **daemon launcher script is missing** from the shared deps dir, even though `node_modules` is fully installed and `embeddings.enabled = true`:

```
$ ls ~/.hivemind/embed-deps/
node_modules/ package.json # <-- embed-daemon.js is absent
$ hivemind embeddings status
Daemon: (not present)
```

`SHARED_DAEMON_PATH` = `~/.hivemind/embed-deps/embed-daemon.js` (`src/embeddings/standalone-embed-client.ts:39`). `hivemind embeddings install` is what deposits it (`src/cli/embeddings.ts:123-131`, "Always (re)deposit the canonical embed-daemon.js"), copying from `pkgRoot()/embeddings/embed-daemon.js`. On this machine that file never landed — most likely lost across a plugin version bump (the deps dir survived, the launcher did not).

The failure then cascades through the recall hook:

1. `recall.js` runs as a **synchronous** `UserPromptSubmit` hook with `"timeout": 2` (`hooks/hooks.json`). Its internal budget `RECALL_BUDGET_MS` defaults to 1500 ms (`src/hooks/recall.ts:63`), designed to finish under the 2 s cap.
2. With `embeddings.enabled` and `HIVEMIND_SEMANTIC_SEARCH` unset, it takes the semantic path and calls `trySpawnDaemon(SHARED_DAEMON_PATH)` (`src/embeddings/standalone-embed-client.ts:178`).
3. The daemon entry file doesn't exist, so the spawn produces no listening socket. `waitForSocket()` (`:259`) loops until its deadline instead of failing fast, so the Node process **hangs**. The internal 1500 ms budget logs a `timeout` event but does **not** exit the process (a handle stays open), so it lingers well past 2 s and the harness hard-kills it, discarding output.
4. Because the process is killed each time, the daemon never comes up and stays down → every subsequent prompt re-hangs. Chronic.

Measured hang (near-zero CPU, pure I/O wait — confirming it's blocked on the absent socket, not compute):

```
recall.js, embeddings enabled, daemon launcher missing:
real 5.12s user 0.18s sys 0.08s (cold)
real 40.5s user 0.19s sys 0.06s (subsequent)
```

## Secondary issues (surfaced after manually restoring embed-daemon.js)

Copying the launcher back in from the plugin bundle (`cp .../bundle/embeddings/embed-daemon.js ~/.hivemind/embed-deps/ && chmod 755`) fixes the hang, but two problems remain that make semantic recall unreliable inside this 2 s-capped synchronous hook:

- **Daemon does not persist between hook invocations.** Runs intermittently take ~20 s — a full cold model reload — meaning the daemon dies between prompts (the 2 s hook-kill likely orphans the freshly spawned child before it detaches).
- **Even warm, recall is 1.6–2.35 s**, i.e. routinely at or over the 2 s cap (Node startup + bundle load ~0.3 s sit on top of the 1.5 s embed+query budget):
```
warm semantic recall: real 1.64s / 1.64s / 2.35s (3rd run trips the 2s cap)
lexical (HIVEMIND_SEMANTIC_SEARCH=false): real 0.16s / 0.16s / 0.34s
```

## Suggested fixes

1. **Self-heal the missing launcher.** When `embeddings.enabled` and `SHARED_DAEMON_PATH` is absent, re-deposit it (or have the plugin `SessionStart`/update step verify+copy it) instead of leaving a permanently broken install. A version bump that keeps `node_modules` but drops `embed-daemon.js` should not be possible.
2. **Fail fast, don't hang.** If the daemon entry file doesn't exist, `trySpawnDaemon`/`waitForSocket` should return immediately and let recall fall back to lexical, rather than looping to the deadline. The recall hook exceeding its own internal budget should hard-exit the process so the harness never has to kill it.
3. **Fix daemon persistence** so it survives across hook invocations (avoid the periodic ~20 s cold reloads).
4. **Reconcile the 2 s cap with semantic latency.** Even a healthy daemon lands ~1.6–2.3 s per call, so semantic recall will intermittently trip the 2 s cap. Consider raising the `recall.js` hook timeout, making it `async`, or gating semantic recall behind a warm-daemon check with lexical fallback otherwise.
5. **Diagnosability:** `hivemind embeddings status` prints `Daemon: (not present)` from an `existsSync(SHARED_DAEMON_PATH)` check on the *script file* (`src/cli/embeddings.ts:305`). That reads as "daemon process not running" when it actually means "launcher file missing." Distinguishing the two would have made this obvious immediately.

## Workaround

For anyone hitting the timeout message: set `HIVEMIND_SEMANTIC_SEARCH=false` (routes recall to the fast lexical path, ~0.2 s, always under the cap). The background summary-embedding path is unaffected (it gates on `embeddings.enabled`, not this env var), so the semantic index still builds once the launcher is restored.