fix: repair pgvector migration to actually convert embedding column from text to vector(1536)

The original migration used a fragile add-copy-drop-rename pattern with
_jsonb casts that silently failed, leaving the embedding column as text.
Replace with a direct ALTER COLUMN TYPE ... USING embedding::vector(1536)
that is fully idempotent and handles all partial states from previous
failed attempts.

DEPLOY-ISSUES-3.md

@@ -0,0 +1,37 @@
+# Search Broken — embedding column not converted to vector type
+
+## Date: 2026-05-12
+
+## Problem
+The search fails with this error:
+```
+operator does not exist: text <=> vector
+HINT: No operator matches the given name and argument types. You might need to add explicit type casts.
+```
+
+## Root cause
+The `NoteEmbedding.embedding` column is still type `text` (old JSON string format), NOT `vector(1536)`.
+The Prisma migration marked itself as applied but the actual column type conversion was never executed.
+The SQL query tries to use the `<=>` cosine distance operator on a text column, which fails.
+
+## Current state
+- pgvector extension IS installed (CREATE EXTENSION worked)
+- But the embedding column was NOT converted from text to vector(1536)
+- There are 102 rows in NoteEmbedding with JSON string embeddings
+- The migration SQL needs to: ALTER COLUMN embedding TYPE vector(1536) using proper casting
+
+## What needs to happen
+1. Check the actual column type: SELECT column_name, data_type, udt_name FROM information_schema.columns WHERE table_name = 'NoteEmbedding' AND column_name = 'embedding';
+2. The migration SQL must convert the column. The embedding values are stored as JSON strings like "[0.1, 0.2, ...]" — need to strip brackets, then cast to vector.
+3. The conversion SQL should be something like:
+   ALTER TABLE "NoteEmbedding" ALTER COLUMN embedding TYPE vector(1536) USING embedding::vector(1536);
+   OR if stored as JSON string:
+   ALTER TABLE "NoteEmbedding" ALTER COLUMN embedding TYPE vector(1536) USING (replace(replace(embedding, '[', ''), ']', ''))::vector(1536);
+4. Also check if the tsvector column and trigger on Note table were created properly.
+5. The semantic-search.service.ts code uses $queryRawUnsafe with <=> operator — make sure the SQL is correct for pgvector.
+
+## Files to check/fix
+- prisma/migrations/20260512120000_pgvector_and_fts_search/migration.sql — the actual migration SQL
+- lib/ai/services/semantic-search.service.ts — the search service using vector queries
+- lib/ai/services/embedding.service.ts — embedding service
+- schema.prisma — NoteEmbedding model