feat(tool-pwsh): teach the confined named-pipe capture boundary to the model

Under read-only and workspace-write the Windows ACL sandbox leaves
programs unable to open named pipes, so a piped-stdio spawn fails with
EPERM. State that boundary in the pwsh tool description next to the
ConstrainedLanguage contract, pin it in the tool tests, and bring the
package README and both implemented Agent Notes current with it.

.agents/notes/implemented/feature/2026-08-08-windows-acl-restricted-token-sandbox.md

@@ -32,11 +32,11 @@ The [landstrip evaluation](../../rejected/feature/2026-07-26-evaluate-landstrip-
 
 ## Consequences
 
-Bought: write-only confinement with no new OS floor (`CreateRestrictedToken` predates the mxc releases by two decades), reads/network/process visibility untouched exactly as the mode vocabulary requires, and fail-closed errors carrying the API name and the exact Win32 code. Cost: no read-side or network isolation; console isolation unavailable (hidden-console children die with `STATUS_DLL_INIT_FAILED`; children share the host console); standing ACE mutations on the granted roots (caller-owned directories; workspace ACEs stand forever by design — the reuse cache, invisible residue when a workspace is renamed — temp ACEs revoked by provider dispose, self-healing across restarts via the durable per-session record — whose immediate flush precedes the ACEs, within the flush latency); grant materialization is an EAGER full-tree propagation (`SetNamedSecurityInfoW` walks every descendant immediately — tens of seconds on large workspaces), paid once per workspace per machine by the per-workspace identity; CIM is unavailable in BOTH confined modes (AuthUsers dropped from both lists — the WMI namespace security check fails, and `Get-ComputerInfo` silently returns incomplete results) as the price of closing the C:\-root tree-creation escape in both; FAT-class (non-ACL) targets outside the granted roots remain writable under both modes (no security descriptors to intersect — a legacy residue treated as unsupported, warn-only, documented in the README); NULL-DACL directories are not identity-preserving under a grant+revoke round-trip (documented edge, the POC shares it); `whoami` and token-inspection cmdlets fail under the restricted token (diagnostic noise, documented); and BOTH confined modes run `pwsh` in ConstrainedLanguage mode — the restricted token trips PowerShell's lockdown detection, so `Add-Type`, non-core .NET statics (`[System.IO.*]::`, `[math]::`), COM objects, and reflection fail with "only core types" errors while `-f` formatting, property access, and core cmdlets/types keep working, and the language mode cannot be lifted back to FullLanguage from inside — taught to the model in the pwsh tool description and documented in the package README's Known Limitations.
+Bought: write-only confinement with no new OS floor (`CreateRestrictedToken` predates the mxc releases by two decades), reads/network/process visibility untouched exactly as the mode vocabulary requires, and fail-closed errors carrying the API name and the exact Win32 code. Cost: no read-side or network isolation; console isolation unavailable (hidden-console children die with `STATUS_DLL_INIT_FAILED`; children share the host console); standing ACE mutations on the granted roots (caller-owned directories; workspace ACEs stand forever by design — the reuse cache, invisible residue when a workspace is renamed — temp ACEs revoked by provider dispose, self-healing across restarts via the durable per-session record — whose immediate flush precedes the ACEs, within the flush latency); grant materialization is an EAGER full-tree propagation (`SetNamedSecurityInfoW` walks every descendant immediately — tens of seconds on large workspaces), paid once per workspace per machine by the per-workspace identity; CIM is unavailable in BOTH confined modes (AuthUsers dropped from both lists — the WMI namespace security check fails, and `Get-ComputerInfo` silently returns incomplete results) as the price of closing the C:\-root tree-creation escape in both; FAT-class (non-ACL) targets outside the granted roots remain writable under both modes (no security descriptors to intersect — a legacy residue treated as unsupported, warn-only, documented in the README); NULL-DACL directories are not identity-preserving under a grant+revoke round-trip (documented edge, the POC shares it); `whoami` and token-inspection cmdlets fail under the restricted token (diagnostic noise, documented); and BOTH confined modes run `pwsh` in ConstrainedLanguage mode — the restricted token trips PowerShell's lockdown detection, so `Add-Type`, non-core .NET statics (`[System.IO.*]::`, `[math]::`), COM objects, and reflection fail with "only core types" errors while `-f` formatting, property access, and core cmdlets/types keep working, and the language mode cannot be lifted back to FullLanguage from inside — taught to the model in the pwsh tool description and documented in the package README's Known Limitations; BOTH confined modes also deny named-pipe opens — libuv's piped-stdio spawns fail with EPERM (the POC-documented "no output redirection" boundary; inherited/ignored stdio and anonymous pipes work) — documented in the package README's Known Limitations and taught to the model in the pwsh tool description.
 
 ## Testing
 
-The product-visible Windows roster flip is win32-only, so the keyless snapshot fixtures — which must replay on macOS/Linux — cannot cover it; the bundle composition specs ([`base.spec.ts`](../../../../packages/bundle/base/tests/base.spec.ts), [`windows-shell.spec.ts`](../../../../apps/cli/tests/windows-shell.spec.ts)) plus the win32 real-runner suites (`packages/sandbox/sandbox-windows-acl/tests/`, `packages/bash/pwsh-sandbox/tests/`) are the substitute evidence, and the CI Windows lane owns the assembled signal. The grant machinery is pinned cross-platform by `packages/sandbox/sandbox-local/tests/acl-session.spec.ts` (record fold/provision with the ownership binding — a fork's copied parent record never provisions the child — tamper validation on the workspace/temp paths, one-shot materialization with the immediate-flush kick, exclusive temp creation with reparse-point rejection, fork/resume temp reuse, the standing-vs-revocable lifecycle across dispose and the mode-switch cycle, and the derived-SID argv contract — with the Win32 surface mocked) and on win32 by `workspace-sid.spec.ts` (derivation determinism/shape/distinctness), `grant.spec.ts` (real-DACL materialization: revocable paths revoke on dispose, standing paths survive it), the `acl.spec.ts` idempotent-grant fast-path and standing-ACE-after-dispose contract, the `failure-paths.spec.ts` suspension-orphan regression (AssignProcessToJobObject failure terminates the child), and the `runner.spec.ts` `--write-sid` contract (caller-owned grants, private temp subdir through TMP/TEMP, both-mode CIM-denial probes, the mode-downgrade regression — a standing grant ACE is inert under read-only and effective again on re-upgrade — the ambient-writable Public-probe regression (a C:\Users\Public subdirectory write is denied under both modes), and the ConstrainedLanguage pins in both modes). The runner-failure classification is exit-gated on 127 (a confined command that merely prints the `windows-acl-run:` signature on a non-127 exit is never misclassified as "the command did not run" — pinned in the pwsh-sandbox helper suite).
+The product-visible Windows roster flip is win32-only, so the keyless snapshot fixtures — which must replay on macOS/Linux — cannot cover it; the bundle composition specs ([`base.spec.ts`](../../../../packages/bundle/base/tests/base.spec.ts), [`windows-shell.spec.ts`](../../../../apps/cli/tests/windows-shell.spec.ts)) plus the win32 real-runner suites (`packages/sandbox/sandbox-windows-acl/tests/`, `packages/bash/pwsh-sandbox/tests/`) are the substitute evidence, and the CI Windows lane owns the assembled signal. The grant machinery is pinned cross-platform by `packages/sandbox/sandbox-local/tests/acl-session.spec.ts` (record fold/provision with the ownership binding — a fork's copied parent record never provisions the child — tamper validation on the workspace/temp paths, one-shot materialization with the immediate-flush kick, exclusive temp creation with reparse-point rejection, fork/resume temp reuse, the standing-vs-revocable lifecycle across dispose and the mode-switch cycle, and the derived-SID argv contract — with the Win32 surface mocked) and on win32 by `workspace-sid.spec.ts` (derivation determinism/shape/distinctness), `grant.spec.ts` (real-DACL materialization: revocable paths revoke on dispose, standing paths survive it), the `acl.spec.ts` idempotent-grant fast-path and standing-ACE-after-dispose contract, the `failure-paths.spec.ts` suspension-orphan regression (AssignProcessToJobObject failure terminates the child), and the `runner.spec.ts` `--write-sid` contract (caller-owned grants, private temp subdir through TMP/TEMP, both-mode CIM-denial probes, the mode-downgrade regression — a standing grant ACE is inert under read-only and effective again on re-upgrade — the ambient-writable Public-probe regression (a C:\Users\Public subdirectory write is denied under both modes), and the ConstrainedLanguage pins in both modes, plus the grandchild-stdio matrix pins — inherited/ignored stdio spawns succeed while piped capture is DENIED in both modes). The runner-failure classification is exit-gated on 127 (a confined command that merely prints the `windows-acl-run:` signature on a non-127 exit is never misclassified as "the command did not run" — pinned in the pwsh-sandbox helper suite).
 
 ## Related