Fix owner-PID false positive when owner runs as different user

ownerAlive() treated EPERM (permission denied) the same as ESRCH
(process not found), causing the server to self-terminate within 60s
whenever the owner process ran as a different user. This affected WSL
(owner is a Windows process), Tailscale SSH, and any cross-user
scenario.

The fix: `return e.code === 'EPERM'` — if we get permission denied,
the process is alive; we just can't signal it.

Tested on Linux via Tailscale SSH with a root-owned grandparent PID:
- Server survives past the 60s lifecycle check (EPERM = alive)
- Server still shuts down when owner genuinely dies (ESRCH = dead)

Fixes #879

RELEASE-NOTES.md

@@ -17,6 +17,7 @@ The subagent review loop (dispatching a fresh agent to review plans/specs) doubl
 
 ### Bug Fixes
 
+- **Owner-PID false positives** — the brainstorm server's `ownerAlive()` check treated EPERM (permission denied) the same as ESRCH (process not found), causing the server to self-terminate within 60 seconds whenever the owner process ran as a different user. This affected WSL (owner is a Windows process), Tailscale SSH, and any cross-user scenario. Fixed by treating EPERM as "alive". (#879)
 - **writing-skills** — corrected false claim that SKILL.md frontmatter supports "only two fields"; now says "two required fields" and links to the agentskills.io specification for all supported fields (PR #882 by @arittr)
 
 ### Codex App Compatibility

skills/brainstorming/scripts/server.cjs

@@ -313,7 +313,7 @@ function startServer() {
 
   function ownerAlive() {
     if (!OWNER_PID) return true;
-    try { process.kill(OWNER_PID, 0); return true; } catch (e) { return false; }
+    try { process.kill(OWNER_PID, 0); return true; } catch (e) { return e.code === 'EPERM'; }
   }
 
   // Check every 60s: exit if owner process died or idle for 30 minutes