B7: researcher/librarian retrieval tools + slim prompts

[aarontrowbridge]

What to build

Replace the researcher/librarian whole-graph front-loading with retrieval tools (amico vault query etc.), and slim those agent prompts accordingly (internal ring only; the product ring's "what next" is the router + L1). (Spec spec-20260708-112732 §3.1, §4.4, §8.8.)

Acceptance criteria

• researcher pulls relevant vault context via query tools instead of eager full-graph reads
• librarian insight-extraction uses retrieval; prompts slimmed
• no loss of brief/insight quality on a sample iteration

Blocked by

• Blocked by B3: migrate vault/device/note bookkeeping verbs #113

Provenance

Design spec (Aaron's vault): spec-20260708-112732; plan plan-20260708-214610 (slice B7).

[aarontrowbridge]

Tool half delivered by B3 (#125): amico vault query — the retrieval tool that replaces researcher/librarian whole-graph front-loading, callable from Claude Code via bash (the CLI-first point). Remaining: slimming the researcher.md/librarian.md prompts to use it — that edits the agent defs currently being migrated in amico#183, so it's HELD until #183 lands (same collision as A5's orchestrator.md and B6). Not building it now = avoiding conflict with an open co-founder PR.