feat: advertise authMethods for ACP registry compatibility

[william0wang]

Summary

Prepares zcode-acp-server for submission to the ACP Registry by advertising the correct authMethods at initialize time and adding the registry submission assets.

Background

The ACP registry CI (verify_agents.py --auth-check) rejects agents that return authMethods: []. The validation requires at least one method with type ∈ {`"agent"`, `"terminal"`} (type omitted defaults to `"agent"`). Our previous empty array would fail with `"No authMethods in response"`.

Our authentication model is agent-managed: the GLM API key is read from `~/.zcode/v2/config.json` by the ZCode backend subprocess — the editor never supplies credentials. This maps to ACP's `AuthMethodAgent` (the same pattern used by `glm-acp-agent`, our closest analog).

Changes

1. `src/server.ts` — correct `authMethods`

```diff

•  authMethods: [],
  

•  authMethods: [
  

•    {
  

•      id: "zcode-credentials",
  

•      name: "ZCode built-in credentials",
  

•      description: "Reads the GLM API key from ~/.zcode/v2/config.json ...",
  

•    },
  

•  ],
  

```
Also removed the meaningless `agentCapabilities.auth: {}` (empty object).

2. `tests/server.test.ts` (new) — 6 tests covering registry gates

• `authMethods` is non-empty (CI gate: rejects `[]`)
• ≥1 method recognisable as `"agent"` type (CI gate: type validation)
• Each method has required `id` + `name` fields
• `initialize` does NOT spawn the backend (CI runs in an isolated HOME with no `config.json` — `initialize` must succeed without credentials)

3. `registry/zcode-acp-server/` — submission assets

• `agent.json` — modelled on `glm-acp-agent`: id/name/version/description/repository/license/distribution.npx
• `icon.svg` — 16×16 monochrome `"Z"` mark, `fill="currentColor"` only (per icon guidelines)

4. `README.md` / `README.zh-CN.md` — "ACP Registry" section

Documents the auth model and points at the submission assets.

Verification

• `pnpm build` — clean
• `pnpm test` — 100/100 passing (94 → 100; +6 new initialize tests)
• `authMethods` JSON shape matches `AuthMethodAgent` in the SDK schema
• `initialize` confirmed not to read credentials (backend is lazy-spawned on first `session/new`, not during handshake)

Subsequent steps (not in this PR)

1. `npm publish` — the `distribution.npx.package` in `agent.json` (`zcode-acp-server@0.1.0`) must match a published npm version. `package.json` already has `bin`/`files`/`main` configured.
2. PR to `agentclientprotocol/registry` — copy `registry/zcode-acp-server/` into a fork of the registry repo and open a PR; CI will validate schema + icon + auth.
3. CI isolated-env smoke test — `python3 .github/workflows/verify_agents.py --auth-check` in the registry repo.

Design note

The `AuthMethodAgent` variant intentionally omits the `type` field — per the registry validator (`client.py:parse_auth_methods`), omitted type defaults to `"agent"`. This is the canonical shape for "agent self-handles auth" and matches every CLI-wrapping agent in the registry (`gemini`, `claude-acp`, `codex-acp`, `glm-acp-agent`, etc.).

[gemini-code-assist]

Code Review

This pull request adds compatibility with the ACP Registry by introducing registry submission assets (agent.json and icon.svg), updating the initialize response in src/server.ts to advertise a built-in agent-type authentication method, documenting these changes in the READMEs, and adding a comprehensive test suite in tests/server.test.ts to verify the initialization response shape. The reviewer suggested updating the repository and website URLs in agent.json to point to the official repository instead of a personal fork.

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