docs: add migration safety guide with pgfence

[flvmnt]

Summary

• Adds a new guide: Analyze migration safety with pgfence (src/content/docs/guides/migration-safety-with-pgfence.mdx)
• Adds navigation entry to _map.json

pgfence (@flvmnt/pgfence on npm) is a Postgres migration safety CLI that analyzes SQL files for dangerous lock patterns. Since drizzle-kit generate produces plain SQL migration files, pgfence can analyze them directly to report lock modes, risk levels, and safe rewrite recipes before migrations reach production.

Guide covers

• Install instructions using the <Npm> component
• The generate-analyze-migrate workflow with Drizzle Kit
• Understanding pgfence output (lock modes, risk levels, safe rewrites)
• Common dangerous patterns detected (non-concurrent indexes, unsafe ALTER COLUMN, etc.)
• CI integration with a GitHub Actions workflow example
• Output format options (CLI table, JSON, GitHub PR markdown)

Why this fits in Drizzle docs

Drizzle Kit generates raw SQL migration files, which makes it a natural fit for static analysis tools. This guide helps Drizzle users catch dangerous DDL patterns (table-level locks, missing CONCURRENTLY, unsafe constraint additions) before deploying, following the same pattern as other ecosystem integration guides.

[Copilot]

Pull request overview

Adds a new Drizzle docs guide describing how to use pgfence to analyze generated SQL migrations for potentially dangerous locking patterns, and exposes the guide in the Guides navigation map.

Changes:

• Added a new MDX guide: “Analyze migration safety with pgfence”.
• Added the guide entry to src/content/docs/guides/_map.json.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/content/docs/guides/migration-safety-with-pgfence.mdx	New ecosystem guide explaining a generate → analyze → migrate workflow and CI integration using pgfence.
src/content/docs/guides/_map.json	Adds the new guide to the Guides navigation list.

Comments suppressed due to low confidence (1)

src/content/docs/guides/migration-safety-with-pgfence.mdx:10

• CodeTabs and CodeTab are imported but never used in this guide. If the docs build/lint checks for unused imports, this can fail CI or add noise. Please remove these imports or add the intended <CodeTabs>/<CodeTab> usage.

import CodeTabs from '@mdx/CodeTabs.astro';
import CodeTab from '@mdx/CodeTab.astro';

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[flvmnt]

Addressed feedback: removed unused CodeTabs/CodeTab imports, pinned pgfence version in all examples, removed hidden Unicode characters.

[flvmnt]

Verified: scanned both files for hidden/bidi Unicode characters (U+200B-U+200F, U+202A-U+202E, U+2066-U+2069, U+FEFF, and all Unicode Cf-category characters) — none found. Previous commit d362d6d already cleaned them. All npx pgfence commands confirmed pinned to @0.2.1 with --yes.