feat: Powershell integration

[nbfritch]

See earlier discussion: #412

This PR adds Powershell support for the activate/deactivate/hook-env commands, allowing support for auto loading like all the existing shells.

Copilot was used to generate a starting point by referencing the src/shell/bash.rs file from fnox and the src/shell/pwsh.rs file from mise. From there, I cleaned up the escaping and added support for displaying the env diff (fnox: +1 FOO / fnox: -1 FOO).

There are 2 possible names for the powershell binary, powershell and pwsh. I elected to use pwsh in the help, in order to avoid lines wrapping around on smaller terminal windows.

For bash/zsh/fish the flow is: eval the output of the activate command, which sets up a hook, which evaluates the output of the hook-env command, which generates code to both set the env variables and also print the env diff. I wanted the powershell to stick to this general flow. However, due to the way powershell evaluates code from the output of a command ( (& cmd) | Out-String | Invoke-Expression) the printed diff gets lost because printing in evaluated commands doesn't bubble up to the parent shell. To solve this hook-env creates a function __fnox_print_changes that contains the Write-Host statements. The powershell code generated by the activate/deactivate command then checks for the existence of that function, evaluates it if it exists, then deletes it.

I tested the powershell integration on the following platforms:

• MacOS 26.4.1 aarch64, powershell 7.6.0
• Windows 10 x86_64, powershell 7.6.0
• Windows 10 x86_64, powershell 5.1.0

Since powershell is different enough from the usual shells (bash,fish,zsh) I left it off the quick start page and lumped it in with nushell in pointing towards the Shell Integration page.

Thank you for your work on this great project!

[gemini-code-assist]

Code Review

This pull request introduces support for PowerShell (pwsh) integration, including documentation updates, CLI help text modifications, and a new Pwsh shell implementation. The review feedback highlights several critical improvements for the PowerShell implementation: correcting environment variable syntax to support non-alphanumeric keys, fixing the escaping logic for single-quoted literals where backticks are not valid escape characters, ensuring the original shell prompt is restored upon deactivation, and using -LiteralPath for robust environment variable removal.

[greptile-apps]

Greptile Summary

This PR adds PowerShell (pwsh/powershell) as a supported shell for the activate/deactivate/hook-env commands, including a new src/shell/pwsh.rs implementation, docs, and bats tests. The implementation correctly handles prompt save/restore in deactivate, single-quote escaping for environment variable values, and the creative __fnox_print_changes function workaround for surfacing Write-Host output through Invoke-Expression.

Confidence Score: 5/5

Safe to merge; all findings are P2 style suggestions that do not affect correctness for typical installation paths.

The implementation is well-structured, tested on three platforms, and the previously flagged deactivate cleanup issue has been resolved. All remaining comments are minor style or defensive-coding suggestions with no present runtime defects.

src/shell/pwsh.rs — minor issues with exe path quoting and Invoke-Expression error suppression worth reviewing before the next major release.

Important Files Changed

Filename	Overview
src/shell/pwsh.rs	New PowerShell shell implementation; core logic is sound with correct prompt save/restore in deactivate(), single-quote escaping in set_env/unset_env, and the __fnox_print_changes workaround for Write-Host output. Minor issues: exe path embedded in double-quoted strings without expansion-safety, and -ErrorAction SilentlyContinue on Invoke-Expression silently swallows errors.
src/shell/mod.rs	Adds pwsh and powershell as aliases to the shell dispatch table; clean and consistent with the existing pattern.
test/shell-integration.bats	Adds four new bats tests covering activate, activate --no-hook-env, hook-env output, and single-quote escaping for pwsh; well-structured and match actual generated output format.
docs/guide/shell-integration.md	Adds a PowerShell tab to the shell-integration guide with the correct activation incantation and link to profile documentation.
src/commands/activate.rs	Doc comment updated to list pwsh as a supported shell; no functional changes.
src/commands/hook_env.rs	Doc comment updated to list pwsh as a supported shell; no functional changes.

Sequence Diagram

sequenceDiagram
    participant PS as PowerShell prompt
    participant FnoxFn as fnox() wrapper
    participant FnoxBin as fnox binary
    participant Hook as _fnox_hook()

    Note over PS: User sources activate script
    PS->>FnoxBin: fnox activate pwsh
    FnoxBin-->>PS: Sets $env:FNOX_SHELL, defines fnox(), _fnox_hook(), patches prompt

    Note over PS: Each prompt render
    PS->>Hook: global:prompt() calls _fnox_hook
    Hook->>FnoxBin: hook-env -s pwsh
    FnoxBin-->>Hook: PowerShell env-set code + optional __fnox_print_changes fn
    Hook->>Hook: Invoke-Expression (sets env vars)
    Hook->>Hook: __fnox_print_changes() calls Write-Host diff
    Hook->>Hook: Remove-Item Function:\__fnox_print_changes

    Note over PS: User runs: fnox deactivate
    PS->>FnoxFn: fnox deactivate
    FnoxFn->>FnoxBin: fnox deactivate (passthrough)
    FnoxBin-->>FnoxFn: PowerShell cleanup code
    FnoxFn->>FnoxFn: Invoke-Expression (restores prompt, removes functions/env vars)

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_{Reviews (3): Last reviewed commit: "Fix formatting for bats test" | Re-trigger Greptile}