docs(pwsh): scope the encoding claim, document the PATH probe and preamble limitation, and fix catalog requires lists

packages/bash/pwsh-local/README.md

@@ -28,7 +28,7 @@ The package root exports the default and named `PwshLocalExecutor` plugin, its `
 The Windows counterpart of `dsh-bash-local`, deliberately mirroring its semantics call-for-call:
 
 - **Spawn per call, no shell state** — every call is a fresh non-interactive `pwsh -Command` (deterministic; no profile files). The `-NoLogo -NoProfile -NonInteractive` flags disable startup banners, profile loading, and prompts that would garble tool output.
-- **UTF-8 I/O pinned** — every command runs with `[Console]::OutputEncoding` and `$OutputEncoding` set to UTF-8 first, so the Windows PowerShell 5.1 fallback (or any host whose console code page is not UTF-8) cannot garble non-ASCII output: the subprocess collector decodes bytes as UTF-8. pwsh 7 defaults to UTF-8 and is unaffected.
+- **UTF-8 output pinned** — every command runs with `[Console]::OutputEncoding` and `$OutputEncoding` set to UTF-8 first, so the Windows PowerShell 5.1 fallback (or any host whose console code page is not UTF-8) cannot garble non-ASCII output: the subprocess collector decodes bytes as UTF-8. Input encoding is left at the host default; pwsh 7 defaults to UTF-8 and is unaffected.
 - **Executable resolution** — `resolvePwshPath` prefers an explicit `pwshPath`, then on Windows probes PowerShell 7's install location, every PATH entry (Microsoft Store installs; surrounding quotes stripped), and Windows PowerShell 5.1 as a legacy last resort, checking `existsSync` on each; elsewhere it falls back to a bare `pwsh` resolved through PATH. Resolution is a pure function of `(configured, env, platform)` and happens once at construction.
 - **Configured budgets over managed groups** — `resolve()` fills `workdir`/`timeoutMs`/`stdoutMaxBytes` from config, and every spawn hands the service explicit byte caps, spill cap, and `graceMs`. Tree termination (taskkill on Windows, process-group signals on POSIX), the post-exit pipe-drain grace, tail-keep truncation, and bounded spill files are [`dsh-subprocess-local`](../../subprocess/subprocess-local/README.md) mechanics. A foreground `BashExecRequest.stdoutMaxBytes` can raise stdout's capture budget for one trusted caller; stderr and background runs still use `maxOutputBytes`.
 - **Timeout and cancel classification** — `run()` fuses its config-clamped timeout with the caller's signal through one deadline; only the executor's own timeout reports `timedOut`, an upstream cancel reports `aborted`, and a self-terminated command reports neither ([timeout-library Agent Note](../../../.agents/notes/implemented/architecture/2026-07-06-timeout-deadline-library.md)). Windows reports forced termination as exit 1 without a signal, so signal-stamped facts (`signal`, `killed` status) are POSIX-only there; the timeout/abort classification is platform-independent.
@@ -50,5 +50,6 @@ No direct invalidation; the named consumer owns any request-prefix changes.
 - **The command string is PowerShell text** — the `-Command` domain has no shell-quoting layer, but a model-facing command is parsed by PowerShell itself, so PowerShell syntax errors are command failures, not launch failures.
 - **A background spawn-failure note is single-delivery** — the subprocess service buffers no output for a process that never ran, so the executor injects `spawn failed: …` into exactly one `readOutput()` delta; a reader that discards that delta cannot recover it.
 - **Windows termination reports no signal** — a force-killed process settles as exit 1 with `signal: null`, so signal-based status classification (POSIX `killed`) does not apply on Windows; `kill()`-initiated stops still stamp `killed` directly.
+- **The encoding preamble precedes the command** — PowerShell requires `param(...)` and `using namespace`/`using assembly` statements at the very top of a script, so a command whose first statement is one of those cannot run under the UTF-8 output preamble; prefix such scripts with a no-op statement (or `& { … }`) first.
 
 Scrub-heuristic and spill-retention caveats live with [`dsh-subprocess-local`](../../subprocess/subprocess-local/README.md), which owns those mechanics.