Phase 2: two-way multi-device sync (#100) + error-signature nudges & panel (#97)

[0bserver07]

Phase 2 of #100 (two-way multi-device sync) and #97 (active-surfacing). Two file-disjoint commits, integrated clean, full suite green.

#100 Phase 2 — two-way multi-device sync

sync pull fetches peers' encrypted mart shards (decrypt, monotonic-generation replay-guard, per-shard content-hash vs cursor → download-changed-only) into <mart>_remote landing tables; sync/merge.py unions local + remote at the stable (provider, slug) grain (SUM), dedups session_mart by session_id with a merge_warnings counter. Exposed via a dedicated routes/sync.py (GET /api/sync/status, GET /api/sync/overview?scope=all-devices) so the default dashboard path is untouched and off the <100ms fast-path. Additive v029 migration (sync_cursors, sync_remote_devices, 5 _remote tables); schema → v29. Default scope=this-device runs no union. 38 tests. (all-devices FE toggle is a documented follow-up; backend + API/CLI are live.)

#97 Phase 2 — error-signature nudge + dashboard panel

New stackunderflow-posttool-nudge (PostToolUse/Bash): after an errored tool result whose signature matches a recurring mined ErrorSignature with resolution_hints, injects a one-line hint under the same governance as Phase 1 (dedupe/cap/cooldown/adaptive-quieting) — emits only additionalContext, never blocks. POST /api/patterns/dismiss writes the exact Tier-1 governance fingerprint (round-trip tested). A "What almost bit me" section in the Health tab lists recent would-have-fired nudges with dismiss controls. Default-off. 43 tests.

Verification

• Full suite: 4083 passed, 2 skipped · ruff --select E,F clean · tsc typecheck clean · vite build (panel bundled) · version guard green · test_pricing_invariants green
• Fully file-disjoint (sync = backend; nudges = hooks + FE); crypto/pull tests gate on pyrage
• CHANGELOG [Unreleased] documents both

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