Remove personal home paths

[kat3samsin]

What changed

• Derive SkimpyClaw report paths from the current user home directory.
• Derive the default Obsidian vault path from homedir() while preserving the existing environment override.
• Remove the personal home directory from the Discord task test fixture.

Why

The public repository contained machine-specific /Users/katre paths. They exposed personal environment details and made the defaults unnecessarily tied to one macOS account.

Impact

Runtime locations remain unchanged for the current user, while clean installations resolve paths for their own account. No tracked source file retains the personal path literal.

Validation

• pnpm build
• pnpm test — 83 files, 982 tests passed
• Focused suites — 3 files, 39 tests passed
• gitleaks staged-diff scan — clean
• Claude review — no blockers

Manual testing

1. Request an existing Chief newspaper and confirm the local artifact link resolves under ~/.skimpyclaw/reports/chief-daily-reader.
2. Run the Mayora artifact repair path and confirm it uses the current home directory.
3. Run morning without SKIMPYCLAW_OBSIDIAN_VAULT_ROOT and confirm Daily Note and Digest paths resolve under the current users Obsidian vault.