feat: Make snapshot functionality project-aware

[arnoli777]

This commit refactors the snapshot functionality to be project-aware. Snapshots are now stored in project-specific subdirectories under .codesage/snapshots/.

The following commands have been updated to support project-specific snapshots:

• snapshot
• diff
• governance-plan
• llm-suggest
• jules-prompt

These commands now require a --project option to specify the project context. The snapshot create command can also override the project name with an optional --project flag.

The history-* commands were investigated and found to be using a separate, legacy snapshot system that is already project-aware. Therefore, they were not modified.

Additionally, the repository has been cleaned up by removing temporary test files and adding them to the .gitignore file. Test fixtures have been moved to the tests/fixtures directory.

[github-actions]

CodeSnapAI Scan Results

Found 22 high severity issues.

• codesage/semantic_digest/shell_snapshot_builder.py:66: Empty exception handler (common LLM artifact)
• codesage/rules/jules_specific_rules.py:60: Empty exception handler (common LLM artifact)
• codesage/rules/jules_specific_rules.py:92: Empty exception handler (common LLM artifact)
• codesage/rules/jules_specific_rules.py:130: Empty exception handler (common LLM artifact)
• codesage/rules/jules_specific_rules.py:156: Empty exception handler (common LLM artifact)
• codesage/rules/jules_specific_rules.py:202: Empty exception handler (common LLM artifact)
• codesage/rules/jules_specific_rules.py:225: Empty exception handler (common LLM artifact)
• codesage/rules/jules_specific_rules.py:256: Empty exception handler (common LLM artifact)
• codesage/rules/jules_specific_rules.py:280: Empty exception handler (common LLM artifact)
• codesage/rules/jules_specific_rules.py:304: Empty exception handler (common LLM artifact)

...and 12 more.