feat(wsl): let an idle WSL distro stop once its server idle-exits (#33084)

* feat(wsl): let an idle WSL distro stop once its orcad idle-exits

The WSL host's holder kept the distro (and the WSL VM) running after Orca quit, even with
nothing running in it. orcad now leaves a release request in ~/.orca when a managed idle stop
retired its terminal daemon; the holder waits for that orcad to exit, claims the request and
ends, so WSL can stop the distro. Live terminals, working agents, enabled automations or a
returning client keep the distro held as before. A host whose distro is stopped at startup
reads as stopped instead of unreachable, and the real-WSL lane gains a phase that proves the
release and records memory.

* fix(wsl): key the holder release on the WSL-host launch marker; name the lane phase

The real-WSL lane showed orcad idle-stopping with its daemon retired while the distro stayed
up: the setsid'd orcad's environment is not guaranteed to carry WSL_DISTRO_NAME, so the
release request was never written. Use ORCA_WSL_ORCAD_HOST, which only WSL-host launches set.
Phase 3 now carries its phase name and path filter, and records what kept a distro running.

* test(wsl): dispose the idle-release lane's guest transports

Each guest command left its exec loop running, a wsl.exe client that kept the distro up after
the holder had already let go (the receipt showed no holder, no orcad, no request left).

* test(wsl): record which wsl.exe clients keep the idle-release lane's distro up

* test(wsl): satisfy the flaky-test ratchet; feed the new idle port in the release test

* test(wsl): snapshot guest processes after launch to find what holds the session

* test(wsl): locate the step that leaves the zombie holding the idle distro

* test(wsl): log the idle-release lane's guest commands with times to place the zombie

* test(wsl): follow the remote runtime client's move

* test(wsl): record when each leftover WSL session init started

* fix(wsl): keep the distro while the user still runs anything, and never trip on the request file

Review of #33084:
- The holder now checks, before claiming a release, that no process of the user runs outside
  the holder itself (session plumbing aside: systemd --user, (sd-pam), dbus-daemon). A detached
  tmux, nohup job or dev server keeps the distro; it fails toward holding.
- A new holder drops any request left from before it started, so an older orcad's request can
  never end a holder a client just asked for.
- orcad touches the request file only for WSL-host launches and never throws over it.
- The real-WSL lane proves a detached job keeps the holder and its request, and the distro
  stops once the job ends.

* fix(wsl): a running container keeps the distro, whoever owns its shim

Docker's containerd-shim processes run as root, so the user-only scan missed them and a
release would have stopped running containers. Any containerd-shim process now keeps the hold.

* fix(wsl): read each process status only up to Uid; document what keeps the hold

Delta review of #33084: dash reads a status file a byte at a time, so stop at Uid. Document
that a root default user never releases, that per-user agents hold it, and the hidepid
exception. The lane's pkill no longer matches the shell running it.

.github/workflows/wsl-orcad-e2e.yml

@@ -34,6 +34,7 @@ on:
       - '!**/*.test.ts'
       - '!**/*.test.tsx'
       - 'src/main/wsl/wsl-orcad-real-distro-lane.test.ts'
+      - 'src/main/wsl/wsl-orcad-real-distro-idle-release-lane.test.ts'
       - '.github/workflows/wsl-orcad-e2e.yml'
       - 'config/ci/wsl-lifecycle/**'
       - 'config/ci/windows-lifecycle-receipt.ps1'
@@ -340,6 +341,16 @@ jobs:
         run: |
           node node_modules/vitest/vitest.mjs run --config config/vitest.config.ts src/main/wsl/wsl-orcad-real-distro-lane.test.ts --reporter=verbose 2>&1 | Tee-Object (Join-Path $env:ORCA_WSL_ORCAD_LANE_RECEIPTS 'survive.log')
           if ($global:LASTEXITCODE -ne 0) { throw "survive phase failed: $global:LASTEXITCODE" }
+      # R40: with no terminal left, orcad idle-exits and the holder lets the distro stop on its own.
+      - name: 'Phase 3: idle orcad releases the distro'
+        timeout-minutes: 15
+        env:
+          ORCA_RUN_WSL_ORCAD_LANE: '1'
+          ORCA_WSL_ORCAD_LANE_PHASE: idle-release
+          ORCA_ORCAD_TEMPLATE_PATH: ${{ runner.temp }}/orcad-template
+        run: |
+          node node_modules/vitest/vitest.mjs run --config config/vitest.config.ts src/main/wsl/wsl-orcad-real-distro-idle-release-lane.test.ts --reporter=verbose 2>&1 | Tee-Object (Join-Path $env:ORCA_WSL_ORCAD_LANE_RECEIPTS 'idle-release.log')
+          if ($global:LASTEXITCODE -ne 0) { throw "idle-release phase failed: $global:LASTEXITCODE" }
       - name: Real desktop agent configuration is unchanged
         if: always()
         run: |
@@ -379,7 +390,7 @@ jobs:
         run: |
           $dir = $env:ORCA_WSL_ORCAD_LANE_RECEIPTS
           $lines = @("### WSL orcad lane (${{ matrix.family }}) — $env:ImageOS $env:ImageVersion", '')
-          foreach ($phase in 'launch', 'survive') {
+          foreach ($phase in 'launch', 'survive', 'idle-release') {
             $file = Join-Path $dir "$phase.json"
             if (Test-Path $file) { $lines += "#### $phase", '```json', (Get-Content $file -Raw), '```' }
           }