fix(operations): per-project git sync + completion receipts in brief (S2, S3)

Brief.Git was a single GitSync read from ORCHESTRA_DATA (never a git
checkout), and completions were counted but discarded their report_ref/
receipt. Brief.Git is now keyed by project ID and built from each
project's real repo; GitSync gained Ahead/Behind vs upstream; Brief now
carries Receipts pulled from each TaskCompleted payload.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W1rkJ2hBMybnJctPbcy4tT

progress.md

@@ -208,7 +208,18 @@ Fixed so far:
   entire log from seq 0. `internal/delivery` previously had zero tests;
   added `TestFanoutContinuesAfterSendError`.
 
-Not yet started: Codex/opencode completion producers, S2–S3, S7–S11. See
+- **S2 + S3** — `/v1/brief`'s git state used to come from `ORCHESTRA_DATA`
+  (the event-log directory, not a git checkout — always reported
+  `"git unavailable"`), and completions were only counted, never surfaced
+  with proof. `operations.Brief.Git` is now `map[string]GitSync` keyed by
+  project ID, built in `main.go` from each `registry.Project.Repo` (falling
+  back to a single `"default"` entry off `ORCHESTRA_REPO` for deployments
+  without per-project repos); `GitSync` gained `Ahead`/`Behind` vs upstream.
+  New `Brief.Receipts []operations.CompletionReceipt` pulls `report_ref`/
+  `receipt` straight out of each `TaskCompleted` event's existing payload.
+  Covered by an updated `TestBuildBrief`.
+
+Not yet started: Codex/opencode completion producers, S7–S11. See
 `AUDIT.md` for the full plan.
 
 **Phase 0 done (2026-07-27):** this box has live TCP reachability to the real