docs: Snapshots, Utils workspace, origin policy, and dialect list

[cursor]

Weekly engineering-docs pass against main (0.2.265). No product-code changes.

Docs added/updated

• USER_GUIDE.md — left-rail names (Compare / Editor / Utils / Snapshots); Utils as its own workspace; Snapshots vs Applies; Same DB warning; partial-grid data compare; Edit/Delete unique-key rule; origin 403 troubleshooting.
• README.md — 14 SQL dialects (+ MongoDB/Redis settings-only).
• DEPLOYMENT.md + .env.example — FOX_ALLOWED_ORIGINS and the literal-IP dev allowlist.
• CONTRIBUTING.md — DIALECTS.md is tracked; E2E sweep timeouts and Lokee 20/min rate-limit helper; dialectFamily().
• ARCHITECTURE.md / CODE_MAP.md / WORKFLOW.md — dialect families, origin guard, unknown fromPort refused at save.
• UNRELEASED.md — workspace and origin-policy notes for the next GitHub Release.
• sql-editor-agent-memory.mdc — Index Management / Clone Table live in Utils, not the SQL Editor sidebar.

Codepaths covered

• UtilitiesView.tsx (Utils workspace; Editor sidebar utilities/files return null)
• LokeeWeaveView / ForceMigrateModal / reversalGate (Snapshots, revert vs force-migrate)
• ActivityRail (Snapshots vs Applies)
• origin-policy.ts (FOX_ALLOWED_ORIGINS, LAN Vite Origins)
• alignResultGridsByKey / migrateKeysSafeForMutatingOps
• dialectFamily() in provider-settings.ts
• assertKnownFromPorts at workflow save
• apps/e2e/scripts/run-all.mjs + rate-limited.ts

Knowledge gaps addressed

• User guide still described a SQL Editor Utilities sidebar and a single History pane.
• README/ARCHITECTURE under-counted dialects (10 vs 14 SQL).
• LAN npm run dev 403s looked like a blank UI with no runbook.
• E2E sweep timeouts and capture/revert 429s had no contributor notes.
• CONTRIBUTING still called DIALECTS.md gitignored.

Verified: npx vitest run packages/shared/src/doc-paths.test.ts (20 passed, 2 skipped).