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/0006-sync-entity-checksum.md

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+# ADR 0006: Sync Entity Checksum for Server/Client Parity
+
+Date: 2026-03-16
+Status: Accepted
+
+## Context
+DB sync currently treats matching `t` values as the main convergence signal.
+That is necessary, but it is not sufficient to guarantee that the client and
+server represent the same block graph.
+
+We have seen cases where temp-id handling and rebase bugs produced logically
+divergent entities while `t` still advanced normally. In those cases, the
+server and client could believe they were in sync even though some entities had
+different content or references.
+
+We need a cheap parity check that works on both the frontend worker and the
+Cloudflare Worker, and the server must stay within a 128 MB memory limit.
+
+## Decision
+1. Add a shared DB sync checksum over block entities only.
+2. The compared attrs depend on whether the graph is E2EE:
+   - Unencrypted graphs compare:
+     - `:block/uuid`
+     - `:block/title`
+     - `:block/name`
+     - `:block/parent`
+     - `:block/page`
+   - E2EE graphs compare:
+     - `:block/uuid`
+     - `:block/parent`
+     - `:block/page`
+3. Reference attrs are normalized to referenced block UUID strings before
+   hashing, so client/server entity ids do not affect the result.
+4. Runtime checksum is maintained incrementally from changed entities in tx
+   reports and persisted locally:
+   - client stores it in client-op metadata
+   - server stores it in `sync_meta`
+5. A full recompute checksum path is kept for simulation and test verification.
+6. The server includes the checksum in state-bearing sync responses:
+   - `hello`
+   - `pull/ok`
+   - `tx/batch/ok`
+7. The client compares the remote checksum against its local checksum only when
+   sync is expected to have converged:
+   - local `t` equals remote `t`
+   - no pending local txs
+   - no inflight upload txs
+8. On mismatch, the client fails fast with `:db-sync/checksum-mismatch` instead
+   of silently continuing with a divergent graph.
+
+## Consequences
+- Positive:
+  - Matching `t` is now backed by entity-level parity over the core sync attrs.
+  - Runtime checksum is fast and memory-light on both client and server because
+    it does not rescan the whole graph on each compare.
+  - Divergence is detected immediately at the sync boundary instead of surfacing
+    later as harder-to-debug invalid entities.
+- Negative:
+  - The checksum is a fast additive hash, not a cryptographic digest.
+  - E2EE graphs intentionally do not compare encrypted title/name fields.
+  - It intentionally ignores attrs outside the sync-invariant set above.
+  - Mismatch handling is fail-fast in this change; it does not automatically
+    repair a divergent graph.
+
+## Verification
+- Frontend worker coverage:
+  - `bb dev:test -v frontend.worker.db-sync-test/hello-checksum-mismatch-fails-fast-test`
+  - `bb dev:test -v frontend.worker.db-sync-test/pull-ok-out-of-order-stale-response-is-ignored-test`
+- Sim parity coverage:
+  - `bb dev:test -v frontend.worker.db-sync-sim-test/two-clients-cut-paste-random-sim-test`
+- Sync compatibility coverage:
+  - `bb dev:test -v frontend.worker.db-sync-test/pending-txs-rewrite-old-string-tempids-test`
+  - `bb dev:test -v frontend.worker.db-sync-test/rebase-order-fix-for-new-blocks-does-not-keep-string-tempids-test`