Locus Coeruleus Phase 1: schema + read+CRUD tools (issue #116 follow-up)

[TSchonleber]

Summary

Ships Locus Coeruleus Phase 1 as an additive inspection/CRUD layer: migration 067, LC proposal, five MCP tools, docs, changelog, and tests. LC now has a concrete trigger catalog, activation log, and single-row tonic/phasic state without changing dispatch behavior or writing downstream NE modulators.

Context

LC is the norepinephrine readiness broadcaster that turns surprise, novelty, and explicit alert events into a global gain signal. brainctl already has surprise sources in cerebellum prediction errors and BG TD errors; this PR adds the LC surface those sources will feed in Phase 2.

Parallel to Claude's NB Phase 1 work on branch brain-regions-nb-phase-1.

What's in

• db/migrations/067_locus_coeruleus.sql: lc_triggers, lc_firings, lc_state, required indexes, seed triggers, and schema_version 67.
• agentmemory.mcp_tools_locus_coeruleus: lc_status, lc_fire, lc_register_trigger, lc_signal_history, lc_set_mode.
• mcp_server.py registration and _build_dispatch() introspection helper used by the requested smoke check.
• docs/proposals/locus_coeruleus.md, MCP docs row, coverage tracker update, and CHANGELOG entry.
• init_schema.sql parity for migration 066 plus 067 so fresh installs match migrated installs.

What's NOT in

• No automatic cerebellum/BG/novelty hookpoints.
• No writes to bg_modulators.lc_ne; Phase 1 only reads that dial in lc_status.
• No retrieval, admission, thalamus, or BG behavior changes.
• No NB files touched or staged from Claude's parallel branch.

Test plan checklist

• Applied migration 067 to a /tmp copy of live brain.db and verified tables, seeds, lc_state, and schema_version 67.
• Backed up live DB to /Users/r4vager/agentmemory/backups/brain.db.pre-lc-20260520T033749Z.db, applied migration 067 live, and verified bg_modulators.lc_ne remained 0.5.
• python3 -m pytest tests/test_mcp_tools_locus_coeruleus.py -x.
• python3 -c "from agentmemory.mcp_server import _build_dispatch; d=_build_dispatch(); print([k for k in d if k.startswith('lc_')])" returns all five LC tools.
• Clean LC-only worktree full suite: 2249 passed, 28 skipped, 2 xfailed.

[TSchonleber]

Superseded by #138 (brainctl-consolidation-v2), which already merged this work into main as part of the v2 tool surface consolidation. Closing as redundant.