feat(packaging): add Windows winget manifest (fixes #524)

Adds winget manifest files for publishing beads to Windows Package Manager:
- winget/SteveYegge.beads.yaml (version manifest)
- winget/SteveYegge.beads.installer.yaml (installer config)
- winget/SteveYegge.beads.locale.en-US.yaml (package metadata)
- scripts/update-winget.sh (helper script for updating manifests)

Once submitted to microsoft/winget-pkgs, users can install with:
  winget install SteveYegge.beads

The update-winget.sh script automates manifest updates for new releases.

Closes #524

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

winget/README.md

@@ -0,0 +1,43 @@
+# Windows Package Manager (winget) Manifest
+
+This directory contains the winget manifest files for publishing beads to the Windows Package Manager.
+
+## Installation (once published)
+
+```powershell
+winget install SteveYegge.beads
+```
+
+## Manifest Files
+
+- `SteveYegge.beads.yaml` - Version manifest (main file)
+- `SteveYegge.beads.installer.yaml` - Installer configuration
+- `SteveYegge.beads.locale.en-US.yaml` - Package description and metadata
+
+## Submitting to winget-pkgs
+
+1. Fork https://github.com/microsoft/winget-pkgs
+2. Create directory: `manifests/s/SteveYegge/beads/<version>/`
+3. Copy the three manifest files to that directory
+4. Submit a PR to microsoft/winget-pkgs
+
+Or use the wingetcreate tool:
+```powershell
+wingetcreate update SteveYegge.beads --version <new-version> --urls <new-url> --submit
+```
+
+## Updating for New Releases
+
+When releasing a new version:
+
+1. Update the version in all three manifest files
+2. Update the InstallerUrl in the installer manifest
+3. Update the InstallerSha256 (get from checksums.txt in the release)
+4. Update the ReleaseNotesUrl
+5. Submit PR to microsoft/winget-pkgs
+
+### Getting the SHA256
+
+```bash
+curl -sL https://github.com/steveyegge/beads/releases/download/v<VERSION>/checksums.txt | grep windows
+```