recall: proactive recall silently no-ops on a default install (embeddings opt-in, no lexical fallback, no user signal)

[kaghni]

Proactive recall is semantic-only — bae7bbb1 dropped the ILIKE fallback because unindexed scans blew the 1500ms blocking budget (src/hooks/recall.ts:13-17). That was the right call for latency.

But embeddings are opt-in: a fresh marketplace install has no @huggingface/transformers, so detectStatus() returns no-transformers (src/embeddings/disable.ts:18-22) and SEMANTIC_ENABLED is false (src/hooks/recall.ts:60).

Net effect: on a default install, proactive recall does nothing, forever, with no user-visible signal. The hook runs, gates, finds no embeddings, emits nothing. Nothing tells the user the headline feature is inactive or how to turn it on.

Degradation today:

	embeddings ON	embeddings OFF (default)
Proactive recall	semantic, top-1	completely off
Reactive (VFS grep)	lexical + semantic UNION	lexical — still works
Capture	writes vectors	writes NULL embedding

Suggested fixes, cheapest first:

1. One-time notice via the existing notifications framework: "Proactive recall is off — run hivemind embeddings install to enable it." Fires once, at SessionStart, same channel as the referral nudge.
2. Server-side query embedding — Deeplake embeds the query; no local deps, one extra hop inside the existing budget.
3. Ship a small quantized model in the default bundle, upgrade to nomic on explicit install.

Related but distinct: #184 (upgraders get enabled=false from an unset env var) and #296 (hook hangs when the launcher is missing despite embeddings enabled). This one is about a fresh, correctly-configured install where the feature is simply absent and silent.