Add native Windows support (PowerShell port)

[aclima01]

Summary

Adds Windows support. Herdr's Windows build runs plugin commands with no shell, and a bare
bash resolves to WSL — so bun sync-title.js can't drive the title sync there. This ships
sync-title.ps1, a field-for-field PowerShell port using native ConvertFrom-Json (no Bun/Node),
and routes each manifest item per-OS via platforms.

Validated end-to-end on Herdr 0.7.1-preview / Windows 11 (Windows Terminal + PowerShell): the
refresh action and the event hooks build agent: task (workspace) from herdr pane current,
herdr workspace get, and the Claude/Codex session JSONL, then call herdr terminal title set
(which works fine on Windows once the server is running).

What changed

• sync-title.ps1 (new) — mirrors sync-title.js: same title precedence (pane title → agent
  • custom status → latest user prompt from the session JSONL → agent name → numbered-tab
    fallback), the same (workspace) suffix and 80-char cap, and the same <command-name> / tag
    stripping. Uses Get-ChildItem -Recurse -Filter in place of find, and $env:USERPROFILE
    for HOME.
• herdr-plugin.toml — platforms now includes windows, and every item carries its own
  platforms. The unix entries keep bun sync-title.js (gated to macos/linux); Windows
  entries run powershell -NoProfile -ExecutionPolicy Bypass -File sync-title.ps1. The manual
  refresh action is refresh-win on Windows, because Herdr rejects duplicate action ids even
  across disjoint platforms (duplicate event on triggers are allowed, so each event just gets
  a second, Windows-gated entry).
• README — Windows in Requirements and the refresh-win action id.

Unix behavior is unchanged: those items still run only the original bun command.

Notes

• Windows is Herdr's own "preview / best effort" tier for plugins; this rides on the same
  herdr terminal title set the unix path uses.
• One caveat inherited from the design: the title can include prompt text (already covered under
  Privacy in the README).

🤖 Generated with Claude Code