[Epic] Integrate Jira and GitHub or GitLab evidence

[phamhungptithcm]

Goal

Use external system evidence so gig can explain ticket state with more than branch history alone.

Scope

• Jira issue enrichment
• GitHub or GitLab pull request evidence
• deployment and environment evidence
• build and approval metadata where available

Task Checklist

• define integration boundaries and provider interfaces
• ingest issue-key-linked PR and deployment evidence from GitHub or GitLab
• enrich ticket inspection with Jira issue metadata when configured
• show which environment a ticket is known to have reached
• document required credentials and fallback behavior when integrations are absent

Acceptance Criteria

• gig can distinguish branch presence from deployment evidence
• ticket inspection becomes more useful than commit matching alone
• the tool still works in degraded read-only mode when integrations are not configured

References

• docs/17-product-strategy.md
• docs/18-operating-model.md