fix(pi): claim the status pane when the inherited owner PID is dead (STA-5245) (#16631)

* fix(pi): claim the status pane when the inherited owner PID is dead (STA-5245)

The managed pi/omp/prime-agent status extension suppressed itself whenever
ORCA_PI_STATUS_OWNED held a PID other than its own, with no check that the
owner still existed. A restart leaves the previous owner's PID in the
inherited env, so every later load returned early and the pane stopped
reporting status permanently.

Probe the owner before suppressing. Only ESRCH proves it is gone; any other
probe result keeps suppression so a live foreign owner still cannot
double-report. This mirrors the tri-state in
main/agent-hooks/managed-hook-owner-identity.ts, which the extension cannot
import because it loads inside the pi/omp runtime with no Orca deps.

Also extracts the generated-source test harness into its own module so the
suite stays under the max-lines limit.

* fix(pi): validate inherited status owner pid markers

---------

Co-authored-by: Neil <neil@stably.ai>

.github/workflows/pi-owner-runtime.yml

@@ -0,0 +1,29 @@
+name: Pi owner runtime verification
+on:
+  pull_request:
+    paths:
+      - 'src/main/pi/agent-status-handler-source.ts'
+      - 'tests/tools/pi-owner-runtime-smoke.mjs'
+      - '.github/workflows/pi-owner-runtime.yml'
+  workflow_dispatch:
+permissions:
+  contents: read
+jobs:
+  runtime:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+    runs-on: ${{ matrix.os }}
+    timeout-minutes: 20
+    env:
+      ORCA_BACKGROUND_LAUNCH: '1'
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          persist-credentials: false
+      - uses: ./.github/actions/install-node-dependencies
+      - name: Install pinned extension loader
+        run: npm install --prefix .cache/pi-owner --ignore-scripts --no-audit --no-fund @earendil-works/pi-coding-agent@0.83.0
+      - name: Verify real owner exit and hook delivery
+        run: node tests/tools/pi-owner-runtime-smoke.mjs .cache/pi-owner/node_modules/@earendil-works/pi-coding-agent