TSM-03: codify permissive TS guardrails and hardening schedule

[Justin Hammond (Justintime50)]

Summary

Codifies permissive TypeScript migration guardrails and adds explicit timing/rules for when rename-only conversion ends and type hardening begins.

Changes in this PR

• adds permissive strategy guidance in dev docs (dev-docs/TYPE_STRATEGY.md)
• adds compile-only type compatibility checks (tsconfig.type-tests.json and test/types/permissive_types.ts)
• wires typescript:compat into the typescript pipeline in package.json
• updates dev-docs/TS_MIGRATION_EXECUTION_BOARD.md with:
  • Type-Integration Policy by phase (TSM-00..TSM-91)
  • required hardening checks for TSM-06+
  • deferred typing PR requirements
  • catch-up schedule for hardening already completed foundation layers

Testing

• npm run typescript

Stack Context

Depends on PR #558.