test(pwsh): clarify deadline comment and keep case budget independent

Review feedback: the dsh-terminal-bash product default is 30s, not 300s;
the raised value bounds one send plus the complete startup sequence, so it
must cover the same cold start the tool deadline does. The vitest case
budget stays at its pre-existing 120s: the case-level timeout overrides
the lane --testTimeout, so syncing it to the plugin deadline would make a
stalled partition wait 300s instead of 120s.

packages/shell/tool-pwsh-persistent/tests/loader-composition.spec.ts

@@ -99,7 +99,10 @@ describe.skipIf(!hasPwsh)('persistent pwsh through a real cordis.yml Loader comp
       // PSReadLine + Defender) inside the tool deadline; a 60s bound on the
       // fully loaded self-hosted Windows pool is exceeded often enough to
       // reset the session mid-test (2026-09-01, two runs ~62s each). 300s
-      // matches the product default so cold start no longer races the budget.
+      // matches the dsh-tool-pwsh-persistent product default; the
+      // dsh-terminal-bash value bounds one send plus the complete startup
+      // sequence, so it covers the same cold start (its 30s product default
+      // would not).
       '    timeoutMs: 300000',
       '    disposeGraceMs: 500',
       "- name: '@deepseek-ai/dsh-tool-pwsh-persistent'",
@@ -171,5 +174,5 @@ describe.skipIf(!hasPwsh)('persistent pwsh through a real cordis.yml Loader comp
     const exited = text(await execute('exit', 'exit'))
     expect(exited).toContain('next pwsh call starts from the workspace')
     expect(text(await execute('after-exit', 'Write-Output "$PWD"'))).toBe(root)
-  }, 300_000)
+  }, 120_000)
 })