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.

acp_registry/agent.json

@@ -8,8 +8,9 @@
   "authors": ["Nous Research"],
   "license": "MIT",
   "distribution": {
-    "npx": {
-      "package": "@nousresearch/hermes-agent-acp@0.13.0"
+    "uvx": {
+      "package": "hermes-agent[acp]==0.13.0",
+      "args": ["hermes-acp"]
     }
   }
 }