Allow-list for safe send_input patterns

[rysweet]

Add SAFE_INPUT_PATTERNS allow-list in _validation.py. When input matches only safe patterns (y, n, yes, no, URLs, file paths, /commands, claude launch commands), skip blocklist check. When it contains anything else, require --confirm or high confidence.

Files to modify:

• src/amplihack/fleet/_validation.py
• src/amplihack/fleet/fleet_session_reasoner.py

Requirements:

1. Define SAFE_INPUT_PATTERNS as compiled regex list in _validation.py
2. Patterns: ^(y|n|yes|no)$, URL patterns, file paths, /slash-commands, claude launch commands
3. Add is_safe_input(text) -> bool function
4. When is_safe_input returns True, skip blocklist validation
5. Update fleet_session_reasoner.py to use is_safe_input
6. All 918+ fleet tests must pass
7. Commit changes on this branch

[rysweet]

Fixed by PR #2936 (merged).