feat: add trigger-driven runs, progress comments, and JSON metadata

[activadee]

Summary

This change adds trigger-driven execution controls, execution metadata capture, and optional progress comments for issue/PR workflows in codex-action, while preserving existing prompt / prompt-file behavior for unchanged workflows.

Problem and User Impact

Before this change, users had limited control over when the action should run from GitHub events, limited structured telemetry from codex exec, and no built-in progress signaling on issue/PR threads. That made it harder to run Codex only for specific intents (for example mentions/labels/assignees), harder to consume run metadata programmatically, and harder for collaborators to track in-flight action status.

Root Cause

The action flow only supported static prompt inputs and did not parse JSON event streams from codex exec. It also lacked a first-class progress comment lifecycle and event-context trigger detection pipeline to gate downstream steps.

Fix

The patch introduces a trigger detection stage (trigger-phrase, label-trigger, assignee-trigger) that can derive a prompt from event payload context with optional sanitization. It adds JSON event capture (--json) and metadata extraction for session/usage outputs, plus optional step-summary output. It adds start/finish progress comment updates with sticky-comment support and new action inputs/outputs/documentation. The follow-up review fixes are included: finalize progress comments only when a start comment ID exists, pull issue/PR number from pull_request.number for PR review-style payloads, and paginate sticky-comment lookup to avoid duplicates on long threads.

Validation

I validated the implementation with repository checks:

• pnpm test
• pnpm check
• pnpm build

All commands completed successfully.

[github-actions]

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