Add generic deployment docs and fix stale references

Adds docs/deployment.md, a platform-agnostic guide (any Linux host with
Docker) built around a git-pull based fast-redeploy workflow, replacing the
Proxmox-specific deploy/proxmox_llm_deploy.md which was also stale (old
`persona` field, single-shared-token model predating multi-user auth).

Also: drops the unused DAYBOOK_API_TOKEN from deploy/env.example, documents
the new DELETE endpoint and capabilities `methods` field in docs/api.md and
docs/agent_quickstart.md, and fixes CLAUDE.md's OpenCode note now that
opencode.json is untracked (machine-specific MCP config).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docs/api.md

@@ -333,6 +333,26 @@ Editable fields:
 
 You can only PATCH artifacts your own token owns; others return `404`.
 
+## Delete Artifact
+
+Endpoint:
+
+```http
+DELETE /api/artifacts/{id}
+Authorization: Bearer <your-personal-token>
+```
+
+Removes the artifact's database row and its files (primary file, markdown
+sidecar, and any attached assets). Returns `204` with no body on success.
+
+You can only delete artifacts your own token owns; others return `404`, as
+does a second delete of the same id.
+
+```bash
+curl -X DELETE "http://127.0.0.1:8001/api/artifacts/a1b2c3d4" \
+  -H "Authorization: Bearer <your-personal-token>"
+```
+
 Not editable yet:
 
 | Field | Reason |
@@ -403,7 +423,12 @@ Example response:
   "views": ["rendered", "raw"],
   "raw_supported_for": ["markdown", "html_full"],
   "source_types": ["agent", "person", "system"],
-  "auth": "bearer_token"
+  "auth": "bearer_token",
+  "methods": {
+    "/api/artifacts": ["GET", "POST"],
+    "/api/artifacts/{id}": ["GET", "PATCH", "DELETE"],
+    "/api/assets": ["POST"]
+  }
 }
 ```