feat(harness): project client-owned turns

[chughtapan]

What changed

• enrich the daemon's loopback MCP search_conversations result with each conversation's participants, composed from the existing production list/read behavior
• keep the canonical protocol Conversation and main WebSocket search result unchanged
• let HarnessClient call the MCP read tools, reconstruct current and cross-conversation presentation, and persist stable checkpoints through an injected local KeyValueStore
• expose the existing EnrichedInboundMessage presentation plus a payload-only reply closure bound to the originating conversation
• reuse the channel-owned enrichment projection so the current adapters and Harness path render the same turn shape

Raw MCP events and reply routing remain package-private. This adds no lease, reply token, action ID, duplicate-reply suppression, byte accounting, or runtime track switch.

Stack

• base: feat(harness): add client context reconstruction #945
• read-plane prerequisite: feat(harness): add MCP read plane #944
• presentation-state prerequisite: refactor(client): isolate presentation state #943
• merged receive/reply foundation: Add daemon-backed HarnessClient receive path #942
• upstream v1 control-plane simplification: refactor!: shrink the v1 control plane to a router #924

Validation

• pnpm nx run @moltzap/client:build
• pnpm nx run @moltzap/client:typecheck:tests
• pnpm nx run @moltzap/client:test — 32 files, 231 tests
• pnpm nx run @moltzap/client:lint
• pnpm nx run @moltzap/client:arch:check
• pnpm nx run workspace:format:check
• pnpm nx run workspace:docs:check:no-hardcoded-constants
• pnpm nx run workspace:docs:check:doc-imports-resolve
• focused daemon integration — 3 tests, including direct WebSocket + loopback MCP round trip and no Unix socket
• previously timing-out formatting integration rerun alone — 3 tests passed
• independent final wire/scope review — clean

Nx caching remained enabled.

[chughtapan]

Superseded by #974, which collapses this stack into one PR against main. This branch's commits are all contained in it — nothing is lost, and this thread stays readable. Closing to leave one place to review.