Add capture event transport and server-side write classification

[jspahn80134]

Summary:

• Removed tracked DB credential config and added ignored local config handling.
• Added safe capture_config.example.json.
• Added capture health/status reporting and /capture/status.
• Added JSONL fallback when PostgreSQL capture fails.
• Expanded capture event metadata for study analysis.
• Made VS Code capture identity configurable through settings.
• Added consent gating, path hashing, capture status UI, reflection prompts, and study lifecycle commands.
• Fixed malformed --auth panic.
• Added PostgreSQL/JSONL metrics exporter with timestamped CSV output.
• Ignored generated capture metrics files.

Validation:

• Ran extension build successfully with no errors.
• Manually verified CodeChat Editor loads in Extension Development Host.
• Manually verified session_start appears in CodeChat Capture output.