fix(workflow): catch up missed cron fires

[BluRoot01]

Summary

• persist per-workflow cron cursors so scheduler restarts retain execution progress
• claim due schedule slots atomically before emitting actions, preventing duplicate execution across concurrent ticks
• catch up missed cron fires within a bounded window and record skipped backlog safely
• cover normal due execution, restart catch-up, duplicate prevention, and database persistence

Related issue

• Buzz production issue: buzz://issue?id=3fdeffee9e1aeb6693e13d0fda17d0be50e301a2847143c81a56466df8c4f45f&owner=0f3a6f2f1e2d60769a231ae87b87f56aa9ddf4f3bdbb0a9d264bdc46cf21f614&d=switchboard-zoho-gateway
• No matching upstream GitHub issue found during incident triage.

Migration

Adds migrations/0045_workflow_schedule_cursors.sql. The owner approved this migration for deployment on 2026-09-08. It creates the scheduler cursor table and its cleanup trigger; no existing application data is rewritten.

Testing

• 171 buzz-workflow unit tests passed
• all 6 PostgreSQL scheduler persistence tests passed
• Rust formatting passed
• strict Clippy passed
• independent Sentry review passed
• verified tested commit: 0d05ec6e90087b88fea403aa512779908adf8e80

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-08T23:40:14.910071Z	0d05ec6	PR opened

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[github-actions]

🔐 Codex Security Review

Status: review required for the current range.

The current range is c045321a7fb3ca8939f28519ce7a555a6f597728...0d05ec6e90087b88fea403aa512779908adf8e80.
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[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 0d05ec6e90

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[chatgpt-codex-connector]

Mirror the cursor into the desired-state schema

This defines the cursor relation only in the incremental migration; a repo-wide search confirms that schema/schema.sql contains neither workflow_schedule_cursors nor its reset trigger. Fresh databases created through the repository's pgschema apply path therefore lack this relation, so every cron tick fails in get_or_seed_workflow_schedule_cursor, and community-deletion catalog validation also expects a table that is absent. Add the table, trigger function, trigger, and write fence to the desired-state schema.

AGENTS.md reference: AGENTS.md:L557-L557

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[chatgpt-codex-connector]

Make the global fire budget fair across workflows

When more than 100 schedule instants are due per minute, this fixed-order break permanently starves later workflows: list_all_enabled_workflows orders by created_at ASC, the first 100 minutely workflows consume the entire budget, and those same workflows each become due again before the next tick, so workflow 101 is never visited and its backlog only grows. The cap needs fair rotation or pagination across workflows rather than restarting from the oldest row on every tick.

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