fix(migrations): resolve VCS migration prefix collision (213-215) and unblock deploy (MUL-3772) (#5883)

Renumber the six VCS migrations off the 213/214/215 prefix collisions to a unique contiguous tail 216-221 (tables before indexes), and make 214_chat_session_project idempotent (ADD COLUMN IF NOT EXISTS) so the #5868 rename-induced re-run no-ops instead of crashing. Fixes the red migration lint on main and unblocks the dev deploy.

server/migrations/214_chat_session_project.up.sql

@@ -4,5 +4,11 @@
 -- Create/delete handlers serialize on the project row, project deletion clears
 -- existing references, and daemon claim revalidates workspace ownership before
 -- injecting any context.
+--
+-- IF NOT EXISTS because this migration was first shipped as 213_chat_session_project
+-- and later renumbered to 214 (#5868, dodging a prefix collision). Environments
+-- that already applied it under the old 213 name have the column but not the 214
+-- version row, so the runner re-applies it under the new name; without the guard
+-- that re-run fails with "column already exists" (SQLSTATE 42701) and blocks deploy.
 ALTER TABLE chat_session
-  ADD COLUMN project_id UUID;
+  ADD COLUMN IF NOT EXISTS project_id UUID;

server/migrations/216_vcs_integration.up.sql

@@ -17,7 +17,7 @@
 -- rows below in a single atomic statement). The inline UNIQUE / PRIMARY KEY
 -- constraints stay — they back the ON CONFLICT upsert targets in vcs.sql.
 -- Secondary indexes live in follow-up single-statement CREATE INDEX
--- CONCURRENTLY migrations (214-218), which cannot share a file with these
+-- CONCURRENTLY migrations (217-221), which cannot share a file with these
 -- CREATE TABLEs.
 
 CREATE TABLE IF NOT EXISTS vcs_connection (