chore: yaad backup scheduler + intraprocess lock fix; wire hourly snapshots

[Patel230]

Bumps external/yaad to fbc0466 (PRs #53–58) and wires yaad's new backup scheduler into hawk's session startup.

yaad changes pulled in:

• fix: M1-M11 medium-severity issues from prior code review #53 incremental HNSW updates (fix: resolve all outstanding code quality issues #54 graph restore, fix: resolve err shadow lint failures and bump eyrie submodule #55 backup rotation, chore(submodules): bump eyrie to 5aa1a4f (lefthook co-author strip) #56 docs)
• docs: add sync-clone and commit-clean helpers #57 Store.ScheduleBackups — periodic VACUUM INTO snapshots with rotation
• chore(submodules): bump eyrie to 9da8423 #58 refcounted process lock — fixes a regression where a second in-process NewStore on the same DB was rejected by the flock merged in feat(storage): acquire cross-process lock on database open yaad#47; hawk opens multiple YaadBridges per session and would otherwise lose memory access

hawk wiring:

• external/yaad → fbc0466; go.mod pseudo-version aligned (release-parity check green)
• YaadBridge.EnsureBackups() starts the hourly snapshot loop (~/.yaad/data/backups, keep 7, 30d max age) — called only from configureSessionHeavy (long-lived sessions, via cmd/options.go), never from bare NewYaadBridge() so diagnostics/tests don't leak schedulers
• per-dbDir claim map dedups repeated bridges; YaadBridge.Close() stops the loop and releases the claim (with race-clean regression test)
• bridge now stores dbDir; no interface changes