Initial import of LogDarioSeq baseline

Establishes version control for the personal Logseq DB fork before
starting the server-client architecture migration and domain features
described in docs/agent-guide and the approved implementation plan.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docs/adr/0008-db-sync-simulation-and-replay-coverage.md

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+# ADR 0008: Strengthen DB-Sync Simulation and Replay Coverage
+
+Date: 2026-03-17
+Status: Accepted
+
+## Context
+Recent DB-sync bugs have repeatedly escaped existing unit and simulation tests.
+The failures were only exposed by real user sessions and browser logs, usually
+after long offline editing, undo/redo, delete/recreate, recycle, and
+sequential reconnect flows.
+
+The current test suite has good focused coverage for many individual sync
+helpers, but it still misses several classes of real-world behavior:
+- editor-style multi-step writes such as `insert empty block -> save title`
+- long-lived pending local tx queues
+- undo/redo stacks that survive many sync rounds
+- sequential reconnect flows where one client uploads first and another
+  reconnects later
+- replay of real bad `local-txs` and `remote-txs` captured from logs
+
+That gap makes DB-sync regressions too dependent on manual reproduction and
+post-hoc log analysis.
+
+## Decision
+1. Treat DB-sync simulation as a first-class regression surface, not just a
+   long-running smoke test.
+2. Keep adding deterministic repro tests for every real sync bug that reaches
+   logs or manual QA.
+3. Expand offline multi-client sims to cover:
+   - both reconnect orders
+   - repeated offline/online cycles
+   - long undo/redo stacks
+   - heavier weighting for `delete-blocks`, `move-blocks`,
+     `cut-paste-block-with-child`, `undo`, and `redo`
+4. Add invariant checks during simulation, not only after final convergence:
+   - no malformed pending tx items
+   - no malformed reversed tx items
+   - no invalid lookup-only reverse txs
+   - no DB structural issues such as missing parent/page or page mismatch
+5. Introduce replay-oriented tests that can execute compact fixtures extracted
+   from real logs:
+   - persisted `local-txs`
+   - remote tx batches
+   - reconnect order
+6. Prefer editor-faithful simulation helpers over simplified synthetic ops for
+   block creation and editing.
+7. Keep a small corpus of fixed seeds and exact repro flows in the repository,
+   so future regressions are rerun automatically in CI and local test runs.
+
+## Consequences
+- Positive:
+  - Real sync bugs can be captured once and kept as permanent regressions.
+  - Multi-client offline behavior gets closer to real user workflows.
+  - Broken pending/reverse tx shapes fail earlier and closer to the source.
+  - Investigation time drops because logs can be turned into executable tests.
+- Negative:
+  - Long-running DB-sync tests become more expensive.
+  - Some simulations may still approximate, rather than exactly match, UI
+    timing and browser worker behavior.
+  - The test suite will need ongoing curation so fixed seeds and replay
+    fixtures stay useful instead of becoming noisy.
+
+## Verification
+- Exact repro simulation coverage:
+  - `bb dev:test -v frontend.worker.db-sync-sim-test/two-clients-offline-delete-vs-children-undo-redo-repro-test`
+- Aggressive offline random coverage:
+  - `bb dev:test -v frontend.worker.db-sync-sim-test/two-clients-both-offline-random-undo-redo-sequential-reconnect-sim-test`
+- Reverse/pending tx shape coverage:
+  - `bb dev:test -v frontend.worker.db-sync-test/reverse-local-txs-skips-invalid-reverse-step-test`
+  - `bb dev:test -v frontend.worker.db-sync-test/reverse-local-txs-skips-missing-lookup-entity-step-test`
+  - `bb dev:test -v frontend.worker.db-sync-test/replace-string-block-tempids-rewrites-retract-entity-string-uuid-test`
+- Undo/redo validity coverage:
+  - `bb dev:test -v frontend.undo-redo-test/undo-validation-rejects-invalid-recycle-restore-tx-test`