Adding Pyjamas Conf 2022 - #2

Bug #1: PR Detection Missing
- Added comprehensive PR search that checks for ANY open PR related to
  a conference, not just PRs from the accumulator branch
- Search matches by conference name, slug, URL domain in PR titles,
  bodies, and branch names
- Uses Python for safe string matching to prevent injection issues

Bug #2: Heredoc Delimiter Collision
- Replaced heredoc approach with file-based content storage
- Use base64 encoding for diff content passed between jobs
- Claude Code Action now reads content from temp files using Read tool
- This prevents crashes when scraped content contains delimiter strings,
  special characters, or encoding issues

Bug #3: Duplicate Workflow Triggers
- Changed concurrency group from global to per-conference
- Group key: conference-update-{watch_uuid|url|run_id}
- Different conferences can now run in parallel
- Same conference serializes to prevent race conditions

Additional: Payload Validation
- Added validation step at start of zone-check job
- Fails fast with clear error messages if required fields missing
- Helps diagnose issues like expired PAT tokens
- Provides helpful summary output for debugging

* fix: address conference update pipeline bugs

Bug #1: PR Detection Missing
- Added comprehensive PR search that checks for ANY open PR related to
  a conference, not just PRs from the accumulator branch
- Search matches by conference name, slug, URL domain in PR titles,
  bodies, and branch names
- Uses Python for safe string matching to prevent injection issues

Bug #2: Heredoc Delimiter Collision
- Replaced heredoc approach with file-based content storage
- Use base64 encoding for diff content passed between jobs
- Claude Code Action now reads content from temp files using Read tool
- This prevents crashes when scraped content contains delimiter strings,
  special characters, or encoding issues

Bug #3: Duplicate Workflow Triggers
- Changed concurrency group from global to per-conference
- Group key: conference-update-{watch_uuid|url|run_id}
- Different conferences can now run in parallel
- Same conference serializes to prevent race conditions

Additional: Payload Validation
- Added validation step at start of zone-check job
- Fails fast with clear error messages if required fields missing
- Helps diagnose issues like expired PAT tokens
- Provides helpful summary output for debugging

* fix: use file-based PR detection for conference updates

Instead of fuzzy matching PR titles/branches/bodies, now:
1. Find all open PRs that modify _data/conferences.yml
2. For each, check if the diff actually includes this conference
3. Only skip if a PR genuinely modifies this specific conference

This is more precise and avoids false positives from generic
"conference updates" PRs or branch naming conventions.

* feat: add trigger context to triage workflow

The scheduled extension checker now passes context to triage:
- trigger_reason: extension_check, closing_soon, closing_today, or website_change
- original_cfp_deadline: the CFP date that triggered the check

The triage workflow uses this context to:
- Build a focused prompt for extension checks (vs general website changes)
- Log clearly when no extension was found (avoids spurious PRs)
- Include deadline info in step summary for debugging

This helps distinguish between changedetection.io webhooks (general
website monitoring) and scheduled CFP extension checks (specific focus).

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Co-authored-by: Claude <noreply@anthropic.com>