colonykit-in-colony: a spec-driven dev lane that rides on @colony/core's
TaskThread, ProposalSystem, and MemoryStore instead of introducing
parallel infrastructure.

**packages/spec/** (new workspace package):
  - grammar.ts     — SPEC.md parser / serializer, §G §C §I §V §T §B
                     sections, always-on invariants (`.always` id suffix),
                     FNV-1a stable hash
  - change.ts      — CHANGE.md with §P §S §T §B plus base_root_hash
                     front-matter for three-way merge
  - sync.ts        — three-way merge with three strategies: three_way
                     (default), refuse_on_conflict, last_writer_wins
  - backprop.ts    — failure-signature gate (test-id + error-class +
                     top-3 frames). Promotes a §V draft via
                     ProposalSystem only after promote_after matches
                     (default 2) — no flake-driven invariant churn
  - context.ts     — cite-scoped context loader; resolves a §T id to
                     its transitive closure of cites plus §V.always
  - repository.ts  — filesystem ↔ MemoryStore bridge, atomic archive
                     via tempdir-then-rename so a crash mid-move leaves
                     either the archived or the pre-archive state
  - hash.ts        — base_root_hash computation + verification
  - constants.ts   — SPEC_OBSERVATION_KINDS, SPEC_BRANCH_PREFIX

**apps/mcp-server/src/tools/spec.ts** (new):
  Six MCP tools — spec_read, spec_change_open, spec_change_add_delta,
  spec_build_context, spec_build_record_failure, spec_archive — wired
  in via the same `register(server, ctx)` pattern as the other tool
  groups. Uses MemoryStore.addObservation directly for spec-kind
  observations so we don't need to widen TaskThread.post's kind enum.

**skills/**: /co:change, /co:build, /co:check, /co:archive definitions
for Claude Code users who want to drive the spec flow via slash
commands. Not loaded by any runtime — consumed by hand when a user
opts in.

Tests: packages/spec covers grammar round-trip, always-on detection,
stable hashing, cite-scope transitive closure, all four sync conflict
shapes (10/10 green). apps/mcp-server listTools assertion extended
with the six new tools (17/17 green).

This change intentionally does NOT add: colonykit init CLI, token-
budget CI gate, design.md scaffolding, or cross-change concurrent-edit
detection. Prove the core loop on one change before adding surface.