feat: add local doctor checks

docs/command-stability.md

@@ -23,6 +23,7 @@ The following command families are intended to be stable automation surfaces:
 - `geth daemon run`
 - `geth daemon service install|uninstall|start|stop|status|print`
 - `geth status`
+- `geth doctor`
 - `geth node id`
 - `geth backup create|restore`
 - `geth node list|rename|revoke|grant|revoke-grant|endpoint-add|endpoint-revoke`

docs/production-readiness-roadmap.md

@@ -283,15 +283,15 @@ Goal: make production failures diagnosable from the CLI and logs.
   - `[x]` Iroh relay/local-discovery state is visible without exposing
     unrelated config secrets.
 
-- `[ ]` Add `geth doctor`.
+- `[x]` Add `geth doctor`.
   Acceptance criteria:
-  - `[ ]` Doctor detects daemon not running.
-  - `[ ]` Doctor detects stale local socket.
-  - `[ ]` Doctor detects bad config.
-  - `[ ]` Doctor detects missing `ssh-keygen`.
-  - `[ ]` Doctor explains missing grants and endpoint mismatches when enough
+  - `[x]` Doctor detects daemon not running.
+  - `[x]` Doctor detects stale local socket.
+  - `[x]` Doctor detects bad config.
+  - `[x]` Doctor detects missing `ssh-keygen`.
+  - `[x]` Doctor explains missing grants and endpoint mismatches when enough
     local metadata exists.
-  - `[ ]` Doctor has JSON output for scripts.
+  - `[x]` Doctor has JSON output for scripts.
 
 ## Phase 9: Packaging, Upgrade, And Release Discipline