Expose POST /v1/write on the local loopback API (draft posts/articles from the stub)

[telivity-otaip]

Why

personality-protect api is a loopback stub today (GET /health, POST /v1/filter only). Extending it to the product path — write — unblocks a browser extension, editor plugins, and local automation without ever leaving 127.0.0.1.

Context

• Stub lives in src/personality_protect/api.py
• Product path: write / write_article (see cli.py write command)
• Privacy: bind 127.0.0.1 only; never accept remote hosts by default; never upload corpus

Proposed API

POST /v1/write
Content-Type: application/json

{
  "topic": "Contoso Ledger exceptions",
  "points": "- Name one owner\n- Keep the rollout boring",
  "channel": "post",          // or "article"
  "k": 4,
  "adapter": false,
  "profile": "default"
}

Response (Contoso-safe receipt + draft text for local use only):

{
  "ok": true,
  "channel": "post",
  "adapter": "none",
  "text": "…",
  "local_only": true
}

Acceptance criteria

• POST /v1/write drafts via the same code path as the CLI write command
• Supports --channel post|article equivalents
• Rejects empty topic/points with 400
• Still binds 127.0.0.1 only; document that remote bind is out of scope
• /health lists the new endpoint
• Unit tests with a stubbed/mock model (no MLX download in CI) — mirror demo / mock patterns
• README CLI reference updated under Status / API

Out of scope

• Browser extension UI (separate issue)
• Auth / TLS / LAN exposure

Difficulty

Medium — wire existing write path into the HTTP handler + tests.