fix(landing): make d1 migrations idempotent

Summary:
- Make the initial uploads index migration use IF NOT EXISTS.
- Add a release consistency gate that rejects non-idempotent D1 CREATE
  INDEX statements.

Rationale:
- Production D1 already had the old uploads index before Wrangler's
  migration journal was used, so migrations apply could fail on 0001
  before reaching newer migrations.
- Keeping migrations idempotent makes future Cloudflare release gates
  mechanical instead of relying on manual SQL execution.

Tests:
- bash evals/test-release-consistency.sh
- git diff --check

Co-authored-by: Codex <codex@openai.com>

evals/test-release-consistency.sh

@@ -138,6 +138,17 @@ required_paths = [
 for rel in required_paths:
     if not (root / rel).exists():
         errors.append(f'missing issue-sweep asset: {rel}')
+
+# D1 migrations must be idempotent because existing production DBs may predate
+# Wrangler's migration journal. A non-idempotent CREATE INDEX previously made
+# `wrangler d1 migrations apply --remote` fail on 0001 before newer migrations.
+for migration in sorted((root / 'landing/migrations').glob('*.sql')):
+    text_sql = migration.read_text(encoding='utf-8')
+    if 'CREATE INDEX ' in text_sql:
+        for line in text_sql.splitlines():
+            stripped = line.strip().upper()
+            if stripped.startswith('CREATE INDEX ') and not stripped.startswith('CREATE INDEX IF NOT EXISTS '):
+                errors.append(f'D1 migration has non-idempotent index creation: {migration.relative_to(root)}')
 frustration = (root / 'hooks/frustration-trigger.sh').read_text(encoding='utf-8')
 for term in ['TRIGGER_RE', 'PUA Skill Context']:
     if term not in frustration:

landing/migrations/0001_init.sql

@@ -9,4 +9,4 @@ CREATE TABLE IF NOT EXISTS uploads (
   created_at TEXT NOT NULL DEFAULT (datetime('now'))
 );
 
-CREATE INDEX idx_uploads_github ON uploads(github_id);
+CREATE INDEX IF NOT EXISTS idx_uploads_github ON uploads(github_id);