feat(sync): git sync engine in the daemon - origin push/pull (M4)

[vreshch]

M4 - git sync

The local daemon now acts on each vault's origin[]: a debounced commit + push / pull-rebase
cycle per interval, against external git remotes only (GitHub or self-hosted bare repos). The
reserved cloud channel is never touched here.

What ships

• src/sync/ - a small git-exec wrapper (spawns git, cwd = vault path; memory-core keeps its
  own createGit private) + a per-vault cycle: commit-if-dirty -> ensure remote -> fetch ->
  pull-rebase (keeping both sides on conflict) -> push. Every step is tolerant.
• Daemon loop: per-vault timers scheduled from origin[].interval on boot and on vaults.json
  change; sync state exposed at GET /api/sync/status, forced runs at POST /api/sync/run.
  daemon status prints a one-liner per synced vault.
• agentage vault sync [name] - forces a sync now (all origin-carrying vaults, or one). Uses a
  running daemon when present, else runs in-process. Respects --no-daemon.
• vault add --git <remote> now creates a local working copy (path + origin) so a git-synced
  vault is usable end to end.

Key decisions

• Interval unit = SECONDS. The unified schema stores interval as a bare non-negative integer
  with no minutes marker, so seconds is the least-surprising reading and keeps tests fast. Default
  when absent = 300s. interval: 0 = manual-only (excluded from the daemon loop; still syncable
  via vault sync).
• Ignore mechanism = .git/info/exclude (not per-command pathspecs). It is the robust,
  idempotent choice: matching untracked files are never staged by add -A, and it leaves no
  committed .gitignore in the user's vault. Absent ignore -> defaults ['.obsidian/', 'data.json']; a set value REPLACES the defaults; [] = sync everything.
• Conflict semantics = keep both sides, zero lost writes. A rebase probes for a true conflict
  (clean replay stays linear). On conflict: abort the rebase, capture each conflicted file's remote
  side, merge remote in with content conflicts auto-resolved to the local side (-X ours, so
  remote's non-conflicting changes are still merged), then write each remote copy alongside as
  <file>.conflict.md (never clobbered - a numeric suffix is added). Local content stays in
  <file>; the result is a push-able, descendant-of-remote history.
• Lock-skip strategy. Git failures are classified from stderr (unreachable | lock | conflict | other). A held index.lock (a concurrent engine mutation) is a clean skip that the next cycle
  catches up - never a crash, never a forced unlock. An unreachable remote is likewise recorded and
  retried. Each target is serialised against itself (an in-process flag - no overlapping cycles).
• CRUD never blocks on sync (V6): writes commit locally and return immediately; the sync loop
  runs on its own timer, so an unreachable remote never blocks a write.

memory-core 0.1.2 ride-along

Bumped @agentage/memory-core ^0.1.1 -> ^0.1.2 (lockfile pins 0.1.2). It fixes no-op writes
erroring on "nothing to commit". No other lockfile churn; TypeScript stays pinned at 5.9.3.

Tests

• Unit (new): planner (target selection, interval mapping, ignore resolution), conflict-file
  naming (dedup + suffix), git-error classification, the full cycle over real temp git repos
  (commit/push, no-op, ignore honored + [], divergence keeps both sides, clean remote merge,
  unreachable), and the manager (scheduling, interval-0 exclusion, per-target serialisation, state).
• E2E @p0 (e2e/sync.test.ts, fully self-contained - local git init --bare, isolated config
  dir, ephemeral daemon port; never the real ~/.agentage or :4243): (a) daemon auto-loop pushes
  a write to the bare remote within one interval; (b) divergence -> <file>.conflict.md + both
  contents preserved + push succeeds; (c) unreachable remote -> write still succeeds, error
  recorded, no crash.
• npm run verify green (203 unit tests). Full e2e green (23 tests) against dev, including the new
  sync tier run 3x locally with no flakes.

Guards

Zero new dependencies (spawns git directly); the R6 package-guard allowlist is unchanged.

[github-actions]

🎉 PR Validation ✅ PASSED

Commit: fc967034301398dcfe3a59559ad91ac265cc5dd8
Branch: feature/m4-git-sync

Checks:

• ✅ Release guard (no version/changelog changes)
• ✅ Dependencies installed
• ✅ Type check passed
• ✅ Linting passed
• ✅ Format check passed
• ✅ Tests + coverage passed
• ✅ Build successful

Ready to merge! ✨

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