Exposes projax's /timeline aggregation (Phase 4a) over MCP-RPC so the
PWA (mAi#228) can fetch it without a session cookie against
projax.msbls.de. Same tool surface m's other agents already use.
## Changes
- web/timeline.go: export TimelineQuery, TimelinePayload, add typed
TimelineArgs + BuildTimelinePayloadFromArgs entrypoint. The web cache
stays scoped to the HTTP handler; MCP path re-aggregates per call.
- mcp/tools.go: register `timeline` tool when a TimelineBuilder is
passed. Output mirrors the web template's shape but stringifies
timestamps to YYYY-MM-DD or ISO-8601 UTC so JSON-RPC consumers don't
need Go time semantics.
- mcp/tools_test.go: existing tests pass nil builder (no behaviour
change to the rest of the tool surface).
- mcp/timeline_test.go: 7 unit tests covering registration, arg
forwarding, error propagation, empty payload, and view serialisation.
- cmd/projax/main.go: pass the running *web.Server as the third arg so
the timeline tool registers on the live server (CalDAV-aware).
- docs/design.md §14: documents the tool, schema, output shape, cache
semantics.
## Out of scope
- Caching the MCP path (rejected — re-aggregation per call is cheap;
divergent cache keys aren't worth invalidation complexity).
- Wrapping CalDAV writes (S2 — separate slice once m greenlights).
- PWA backend bridge + frontend (S2/S3 — m/mAi side, after this deploys).
mAi
8b51746183