Implement adopt-not-replace sync with remote .md file tracking

[TheZupZup]

Summary

Overhaul the sync engine to adopt remote notes into the local database instead of replacing it wholesale. This enables idempotent pulls, preserves local-only work, and tracks remote .md files by their canonical server id to avoid duplicates on re-sync.

Key Changes

• Adopt-not-replace pull strategy: Remote notebooks and notes are now upserted in place rather than wiping the local DB. Running pullRemote() multiple times yields the same row set (idempotent).

• Remote id tracking: Added remote_id and remote_path columns to the notes table (schema v1 → v2) so adopted notes can be matched on subsequent pulls without creating duplicates. Plain Markdown files with synthetic md.<base64> ids are decoded to recover their canonical path.

• Push guard for adopted notes: pushLocal() now skips any note that already carries a remoteId, preventing duplicate creation via the non-idempotent POST /notes endpoint.

• Conflict detection: When a remote note arrives with the same cleaned title as an unrelated local row (different id), both are kept and the local row is marked sync_status='conflict'.

• Timestamp-based merge: When a remote note matches a local one by id, the side with the newer updatedAt wins—except local modified rows beat older remotes to preserve in-flight edits.

• Title cleanup: Extracted cleanRemoteTitle() into a dedicated module to strip .md extensions and WebDAV slug suffixes (__<id-prefix>) that leak into note titles from the filesystem.

• Selective deletion: Synced local notes that disappear from the remote are removed (server-side delete propagates), but local-only and modified notes survive a pull.

• Database migration: Added Schema.onUpgrade() to safely add the new columns when upgrading from v1 to v2.

Implementation Details

• SyncResult now includes notesAdopted count to distinguish newly-adopted remote notes from those already in the local DB.
• _PullCounts and _PushCounts separate the return types for clarity.
• LocalNoteService exposes new upsert and hard-delete methods (upsertNote, upsertNotebook, hardDeleteNote, hardDeleteNotebook) used by the sync engine.
• NoteRepository.getNoteByRemoteId() enables lookup of locally-adopted notes by their remote id.
• Comprehensive test coverage added for adoption, conflict detection, title cleanup, and idempotent re-sync scenarios.

https://claude.ai/code/session_01T83ptxrcqCCk9Yx7WerGUd

[chatgpt-codex-connector]

💡 Codex Review

NexaNote/app/lib/services/sync_service.dart

Lines 83 to 85 in 668dcb6

	if (_isAlreadySynced(nb.syncStatus)) continue;
	await _api.createNotebook(name: nb.name, color: nb.color);
	notebooks++;

Record remote notebook IDs after creating local notebooks

After createNotebook succeeds, the local notebook is left unchanged (sync_status stays non-synced and no server ID mapping is stored), but pullRemote now uses adopt-not-replace semantics. In a normal sync loop, that means the same local notebook is posted again on every subsequent sync(), and each pull adds another remote copy instead of reconciling the original. This regression is introduced by the new merge strategy because the old replace-all pull used to wipe the unsynced local row.

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[chatgpt-codex-connector]

Persist pushed-note linkage to avoid re-posting duplicates

pushLocal posts unsynced notes but ignores the created remote note metadata, so the local row keeps no remoteId and remains non-synced. With adopt-not-replace pull, the returned server note is treated as a different record (often causing a conflict-marked local copy plus adopted remote copy), and the original local note is posted again on the next sync. This creates an unbounded duplicate cycle for newly created local notes.

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