docs: canonicalize current project status and release evidence

[Web-pixel-creator]

Summary

• records the exact PR Harden Direct delivery lifecycle and cost-safe monitoring #121 / 2026-08-08 production release evidence;
• replaces the stale README that still reported 215+ tests and a webhook-only runtime;
• makes CURRENT_STATE.md and OPEN_TASKS.md the explicit operational sources of truth;
• adds DOCUMENTATION_POLICY.md for freshness, historical evidence and worktree hygiene;
• labels the June/July plans and the August 2 release as historical snapshots;
• explains the deterministic safety baseline, its real limitations and the guarded hybrid-AI direction without claiming enterprise readiness.

Verification

• git diff --check passed;
• canonical Markdown files pass Prettier;
• README/AI navigation local Markdown links resolve;
• diff is documentation-only: no source, migration, environment, database or runtime setting changed.

Merge boundary

Do not merge only to test Railway. Production is bound to main with Auto Deploy and Wait for CI, so this documentation-only merge may still start a production deployment. Merge remains a separately approved action after CI/security checks finish.