refactor: remove advertising proof gallery and campaign guide; purge session transcript prompts

Removes the 'Grounded, not guessed' proof gallery link and campaign guide
references from README.md. Deletes docs/advertising/ (index.html, campaign.md)
and tests/test_advertising_assets.py. Removes pROMPT_SESSION_TRANSCRIPT_ANALYSIS.md
and session_transcript_query_prompt.md (working prompts that inspect private
~/.commandcode/ session data). Adds all four filenames to .gitignore.

Author: Coding-Dev-Tools

.gitignore

@@ -132,3 +132,8 @@ uv.lock
 /stats_pm2.txt
 /venv_status.txt
 /r3.txt
+
+# Local Command Code session-transcript analysis prompts — inspect private
+# ~/.commandcode/ session data, never commit these.
+/pROMPT_SESSION_TRANSCRIPT_ANALYSIS.md
+/session_transcript_query_prompt.md