feat(acp-registry): switch to uvx distribution, drop npm launcher

The ACP Registry schema supports uvx as a first-class distribution method
alongside npx and binary. Pointing the registry directly at the existing
hermes-agent PyPI release removes:

- the @nousresearch npm scope (we don't own it)
- a separate npm publish step on every weekly release
- 90 lines of Node launcher + tests in packages/hermes-agent-acp/

The Zed registry now installs Hermes via:

  uvx --from 'hermes-agent[acp]==<version>' hermes-acp

This is the same command the npm launcher was shelling out to anyway, so
end-user behavior is unchanged. Registry CI validates the PyPI URL +
version-pin exact match automatically.

Changes:
- acp_registry/agent.json: distribution.npx -> distribution.uvx
- delete packages/hermes-agent-acp/ entirely
- scripts/release.py: drop npm-launcher bump paths, keep manifest lockstep
- tests/acp/test_registry_manifest.py: assert uvx shape + version pin
- tests/scripts/test_release_acp_registry.py: rewrite for uvx-only shape
- docs (user-guide + dev-guide): drop all npm-launcher references
- delete docs/plans/acp-registry-zed-integration.md (stale, npm-shaped)

Validated against agentclientprotocol/registry agent.schema.json via
jsonschema. hermes-agent==0.13.0 is already live on PyPI.

website/docs/developer-guide/acp-internals.md

@@ -31,7 +31,7 @@ hermes acp / hermes-acp / python -m acp_adapter
   -> acp.run_agent(agent, use_unstable_protocol=True)
 ```
 
-The Zed ACP Registry path launches the same adapter through `npx @nousresearch/hermes-agent-acp@<version>`, which delegates to `uvx --from 'hermes-agent[acp]==<version>' hermes-acp`.
+The Zed ACP Registry path launches the same adapter through `uvx --from 'hermes-agent[acp]==<version>' hermes-acp`, pointed at the `hermes-agent` PyPI release.
 
 Stdout is reserved for ACP JSON-RPC transport. Human-readable logs go to stderr.