feat(agent): address agent-native audit recommendations

Add 6 new agent tools (total now 100):
- list_sources: dedicated source listing (was referenced in 5 errors but missing)
- get_clip_cinematography: read full 22-field analysis for a clip
- update_sequence: update sequence metadata (name, fps, music_path)
- create_sequence: explicitly create empty sequence
- search_internet_archive: wrap existing IA search module
- generate_staccato: beat-driven sequencing via agent

Fix prompt-native issues:
- Remove duplicate Untitled Project gate from ToolExecutor (prompt handles it)
- Move CONFLICTING_TOOLS to ToolDefinition.conflicts_with_workers metadata
- Inject analysis value distributions (shot types, objects, transcripts) into
  system prompt for richer agent context
- Fix selected_source_id truncation (was 8 chars, now full ID + filename)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: dvschultz