[BUG] pathToSlug doesn't sanitize Windows paths — SessionEnd hook fails with mkdir ENOENT

[mathbreder]

Describe the Bug

pathToSlug in packages/han/lib/memory/paths.ts (and the duplicated implementation in packages/han/lib/memory/transcript-search.ts) only sanitizes Unix-style path separators:

export function pathToSlug(fsPath: string): string {
  // Replace path separators and dots with dashes, removing leading slashes
  return fsPath.replace(/^\//, '-').replace(/[/.]/g, '-');
}

On Windows, process.cwd() returns paths like C:\Users\<user>\Projects\example-app, which contain no / and no leading slash — so both regexes are no-ops. The function returns the path essentially unchanged, keeping the drive-letter colon (C:) and backslashes (\). That value is then passed into join(getClaudeProjectsDir(), slug) and mkdirSync(...), which Windows rejects because : is only valid immediately after a drive letter and unescaped \ is treated as a path separator.

This breaks the SessionEnd hook (han hook dispatch SessionEnd) on every session close on Windows, and likely any other path that calls getClaudeProjectPath / getHanEventsFilePath (two-argument form) or transcript-search.ts's pathToSlug — e.g. transcript-filter hook, memory indexing.

To Reproduce

1. Use han on Windows, inside a project directory such as C:\Users\<user>\Projects\example-app.
2. Start and end a Claude Code session with the han core plugin active.
3. Observe the SessionEnd hook failure logged when the session ends.
4. Alternatively, reproduce directly in code:

   import { pathToSlug } from './packages/han/lib/memory/paths.ts';
   pathToSlug('C:\\Users\\user\\Projects\\example-app');

Expected Behavior

pathToSlug should sanitize Windows-style separators too, producing a single valid directory-name component, e.g. C--Users-user-Projects-example-app — consistent with Claude Code's own project-slug convention, which already replaces colons and backslashes.

Actual Behavior

pathToSlug('C:\\Users\\user\\Projects\\example-app') returns the path unchanged ('C:\\Users\\user\\Projects\\example-app'). When used to build a target directory via join(getClaudeProjectsDir(), slug), the resulting string contains a second drive-letter-like segment (C:) partway through, which mkdirSync cannot create on Windows, producing an ENOENT error.

Environment

• OS: Windows 11
• Node version: n/a (han runs as a compiled Bun binary, han-windows-x64)
• han version: 3.19.2 (latest tag at time of writing)
• Installation method: Claude Code plugin (han core plugin)

Logs/Output

SessionEnd hook [han hook dispatch SessionEnd] failed: 1
...
ENOENT: no such file or directory, mkdir 'C:\Users\<user>\.claude\projects\C:\Users\<user>\Projects\example-app'
    path: "C:\\Users\\<user>\\.claude\\projects\\C:\\Users\\<user>\\Projects\\example-app"
    syscall: "mkdir"
    errno: -2
    code: "ENOENT"

Additional Context

• Impact appears limited to the affected hook/feature failing (non-fatal, 5s timeout) rather than crashing the session, but it silently breaks per-project memory/event persistence for every Windows user.
• Existing tests only cover Unix-style paths (test/transcript-search.test.ts: pathToSlug converts paths correctly, pathToSlug handles dots and slashes) — no Windows-path case exists.
• Suggested fix — extend pathToSlug to also strip/replace \ and the drive-letter :, e.g.:

  export function pathToSlug(fsPath: string): string {
    return fsPath
      .replace(/^\//, '-')
      .replace(/^([A-Za-z]):/, '$1') // drop drive-letter colon
      .replace(/[/.\\:]/g, '-');
  }

  The exact output format should match whatever slug convention getClaudeProjectsDir() / Claude Code itself expects, so han-generated directories line up with the ones Claude Code creates. A Windows-path test case should be added alongside the fix to prevent regression.