feat(jira): extend existing orchestrations (#578)

[ayushtr-aws]

Extends an existing Jira-authored orchestration with newly added children through the shared additive extension contract. This is PR 2 of 3 for #580 and is based on #725; #727 builds on this branch.

Area

• cdk - infrastructure, handlers, constructs
• agent - Python runtime / Docker image
• cli - bgagent client
• docs - guides or design sources (docs/guides/, docs/design/)
• tooling - root mise.toml, scripts, CI workflows

Related

Closes #578

Parent: #580

Stack: #725 -> #726 -> #727

Changes

• Handle the shared extended discovery result when a Jira parent is retriggered.
• Create and release only genuinely new child nodes while preserving every existing orchestration row and completed result.
• Reopen terminal orchestrations for added work, keep blocked additions pending, and treat no-new-node retriggers as no-ops.
• Add webhook and store coverage for release, metadata propagation, terminal reopen, and invalid additions.

Verification

• mise run build on the stack head
• Focused and full CDK suites (178 suites, 3,554 tests on the stack head)
• GITLEAKS_RANGE=origin/main..HEAD mise run security:secrets:range

Acknowledgment

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of the project license.