feat: Windows support

[shakedarazi]

Adds Windows support to the herdr-plus plugin. Verified end-to-end against a live herdr 0.7.4-preview on Windows 11 (Go 1.26.2); Linux/macOS behaviour unchanged.

What was needed on Windows

Three platform differences drove the change:

1. IPC is a named pipe, not a unix socket. herdr on Windows exposes its socket API as a named pipe at \\.\pipe\<socketPath> (the on-disk herdr.sock is just a liveness marker). Protocol is identical newline-delimited JSON, no token handshake. Added build-tagged dialHerdr: named pipe on Windows (retrying on ERROR_PIPE_BUSY), unix socket elsewhere. Stdlib only, no new deps.
2. Can't spawn an extensionless PE. CreateProcessW appends .exe, so the binary is herdr-plus.exe and each action/pane gets a -windows twin (herdr requires unique action/pane ids; duplicate event on= differentiated by platforms is allowed). Relative-path spawn resolves against herdr's cwd, so Windows entries shell through powershell -Command "& .\bin\herdr-plus.exe <sub>". Panes omit -NonInteractive (interactive TUIs); actions/events keep it.
3. Shell + quoting differ. Centralized every OS difference into one platform descriptor in shell.go (PowerShell vs sh, PowerShell vs POSIX quoting, pane suffix, {{opener}} = Start-Process/open/xdg-open) — no scattered runtime.GOOS.

Verified

• Cross-OS go build (windows/linux/darwin), go vet ./..., go test ./... all green.
• Plugin links + enables with platforms = [linux, macos, windows].
• Named-pipe transport, action spawn, Projects workspace open (tabs + split panes + startup commands, hostile-value quoting round-trip), and worktree.created → auto-layout all exercised on the live host.
• ~/$VARS expansion unit-tested on Windows.

Also

• expandedWorkingDir now surfaces a home-dir resolution error instead of silently discarding it (a missing USERPROFILE would have resolved ~ to a wrong path).
• goreleaser ships Windows amd64 binaries as .zip.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR adds first-class Windows support to the herdr-plus plugin by introducing Windows-specific IPC dialing (named pipes), centralizing shell/quoting behavior behind a platform descriptor, and updating the plugin manifest and release packaging to include Windows binaries and entrypoints.

Changes:

• Add OS-specific abstractions for shell execution/quoting, pane entrypoint selection, and “open” command templating ({{opener}}).
• Add build-tagged IPC dialing to support Windows named pipes while preserving Unix domain socket behavior elsewhere.
• Update plugin manifest, examples, tests, and GoReleaser packaging to support Windows install/run flows.

Reviewed changes

Copilot reviewed 23 out of 23 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
util.go	Removes POSIX-only shellQuote helper now centralized elsewhere.
shell.go	Introduces platform descriptor (shell, quoting, pane suffix, opener) and helpers.
shell_test.go	Adds cross-platform unit tests for quoting/shell dispatch/entrypoint/opener.
quickactions.go	Uses paneEntrypoint() so the correct pane id is opened per OS.
projectsmodel.go	Switches UI display to use displayWorkingDir() for non-error UI contexts.
projectsmodel_test.go	Adjusts assertions for platform-native path normalization.
projects.go	Uses paneEntrypoint() and propagates expandedWorkingDir() errors when opening projects.
project.go	Makes expandedWorkingDir() return (string, error), adds displayWorkingDir() helper.
project_test.go	Updates tests for expandedWorkingDir() error return and separator normalization.
manifest_test.go	Adds test ensuring manifest includes required Windows entries/commands.
herdrdial_windows.go	Adds Windows dialHerdr() using named pipes with retry on ERROR_PIPE_BUSY.
herdrdial_other.go	Adds non-Windows dialHerdr() using unix domain sockets.
herdr.go	Switches client transport to dialHerdr() to unify Windows/Unix IPC.
herdr-plugin.toml	Adds Windows platform + build step + windows-twin actions/panes/events.
examples/quick-actions/open-working-dir.toml	Uses {{opener}} and updates description to be cross-platform.
examples/quick-actions/open-repo.toml	Replaces hardcoded open with {{opener}}.
examples/quick-actions/google.toml	Replaces hardcoded open with {{opener}}.
examples/quick-actions/google-search.toml	Replaces hardcoded open with {{opener}}.
examples/quick-actions/github.toml	Replaces hardcoded open with {{opener}} and documents it.
action.go	Adds template funcs ({{opener}}) and routes execution via shellCommand().
action_test.go	Updates expected quoting to be OS-specific; adds opener helper test.
action_run_integration_test.go	Adds integration test to validate quoting round-trip through real shells.
.goreleaser.yml	Adds Windows builds and ships Windows archives as .zip.

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