Add graff (Codegraff harness) as an ACP agent

[justrach]

Adds graff/ so Zed and other ACP clients can install the Codegraff harness from the registry.

• id: graff
• version: 0.0.283 (latest tagged GitHub Release archives + SHA-256 from SHA256SUMS)
• cmd: nested ./graff-<triple>/graff (./graff.exe on Windows) with args: ["acp"]
• auth: graff acp initialize advertises Terminal Auth (graff-login / type: "terminal" / args: ["login"]) before credential resolution. authenticate is unused — the client re-spawns graff login.
• icon: 16×16 monochrome currentColor

Source: https://github.com/justrach/codegraff
Recipe: https://github.com/justrach/codegraff/blob/main/docs/acp-registry.md
Issue: justrach/codegraff#613
Release: https://github.com/justrach/codegraff/releases/tag/v0.0.283

Pinned off v0.0.282 → v0.0.283 so the auth matrix can see graff-login on a clean HOME. First-time-contributor workflows (Build & Validate / Lint & Test) still need a registry maintainer to approve — we cannot self-approve that.

[justrach]

Not stuck on our side.

• Branch is now current with main (was ~1600 hourly agent-bump commits behind).
• Listing pinned to tagged v0.0.282 — SHA-256 from that release’s SHA256SUMS, same nested ./graff-<target>/graff cmd.
• initialize already advertises Terminal Auth (graff-login).

Still waiting on a registry maintainer: first-time contributor workflow approval. Build & Validate / Lint & Test will not start until someone with write on this repo clicks Approve. I cannot approve that from the fork.

Once those run green, this is ready to merge. codegraff #613 stays open until the listing lands.

[justrach]

Pinned to v0.0.283. That cut includes ACP pre-auth (graff acp answers initialize and advertises graff-login before keys), so a clean isolated HOME should pass the registry auth matrix.

SHA-256s are from the published SHA256SUMS on https://github.com/justrach/codegraff/releases/tag/v0.0.283.

Build & Validate / Lint & Test still need a first-time-contributor workflow approval — we cannot self-approve.