fix(daemon): enrich watcher sync log with timestamp, filenames, and counts

[sunerpy]

Summary

.codegraph/daemon.log watcher sync lines were too sparse to be useful:

[watcher] sync #1: 1 file(s)

They now carry a timestamp, the changed filename(s), and reindexed/removed counts:

[2026-06-29T07:24:45.643+08:00] [watcher] sync #4: 2 file(s) reindexed, 0 removed — src/added.rs, src/lib.rs

• SyncOutcome gains changed_paths: Vec<String> (reindexed + removed paths, sorted for a deterministic line; the source set is a HashSet).
• The daemon log site prepends an RFC3339 local timestamp (local_timestamp(), panic-free local→UTC→empty fallback), shows {reindexed} file(s) reindexed, {removed} removed, and appends a bounded filename tail (first 10 + (+N more)). The catch-up line gets the same timestamp.
• The [watcher] sync # substring is preserved (the single-watcher test contract).

Scope / invariants

Daemon-runtime logging only — no extraction/resolution/MCP/golden change. SyncOutcome has no serde derive and is in no golden/bench artifact → golden byte-neutral (git diff reference/ empty). The only dependency added is time = { workspace = true } on the daemon crate (a pre-existing workspace dep). No new NodeKind/EdgeKind, no schema migration, node-id formula untouched.

Verification

• make ci green; cargo test -p codegraph-bench green (golden oracle); bash scripts/guardrail.sh green
• New tests: sorted-determinism + empty-when-unchanged (codegraph-watch); extended daemon_single_watcher asserts timestamp + counts + filename while keeping the prefix-count contract
• Hands-on QA: real serve --mcp daemon — edited files produced the enriched line shown above
• Final Verification Wave: F1 (goal/constraint) + F2 (code quality) + F3 (golden/invariant) all APPROVE