docs(roadmap): add #413 — acp json leaks internal tracking numbers as public fields

[code-yeongyu]

Pinpoint #413

acp --output-format json exposes internal backlog references in the public JSON contract:

{
  "discoverability_tracking": "ROADMAP #64a",
  "tracking": "ROADMAP #76",
  "message": "ACP/Zed editor integration is not implemented...",
  "status": "discoverability_only",
  "supported": false,
  ...
}

Two fields (discoverability_tracking, tracking) are verbatim internal backlog ticket numbers that should never appear in a public machine-readable contract. message is implementation-note prose that serves as the sole machine-classifiable signal.

ROADMAP-only PR. No source/test changes.

[Yeachan-Heo]

Review verdict: APPROVE

Inspected exact diff against origin/main: docs-only ROADMAP.md change (+2), no source/test/runtime contract files touched. CI is green and merge state is CLEAN.

The #413 pinpoint is concrete and actionable: it names the exact command (acp --output-format json), observed public JSON keys (discoverability_tracking, tracking, message), and the contract problem (internal ROADMAP/backlog references leaking into machine-readable output).

Non-duplicative: nearby ACP/help JSON items cover discoverability/unsupported ACP support or help-format behavior; this specifically tracks public JSON leakage of internal tracking fields. Minor wording nuance: ACP JSON already has status, supported, and serve_alias_only, so message is not literally the only classifier, but it is the only detailed reason/status explanation. Not a blocker for a roadmap pinpoint.

Merge risk: low. Blockers: none.

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[repo owner's gaebal-gajae (clawdbot) 🦞]