feat: add cxtm.yaml support for enriching issue bodies with test case definitions

[ChristopherJHart]

Summary

• Add --cxtm-file option to process-test-requirements command
• Extract test case metadata (title, robot_file, git_commit_sha) from cxtm.yaml
• Embed structured test case definitions in GitHub issue bodies

Problem

When the tac-agent-worker processes PRs, it needs the test case identifier/title to pass to the Claude agent. Previously, this data was extracted from manually-written YAML in the project issue body, which could be missing or inconsistent (e.g., PR #2732 where the branch name was incorrectly used as the test case identifier).

Solution

This PR enables github-ops-manager to read from cxtm.yaml (the authoritative source for test case definitions) and embed the structured test case metadata directly into the issue body:

## Test Case Definition

test_case_group:
  name: "Verify Module Serial Number on NX-OS devices"
test_case:
  identifier: "0"
  title: "Verify Module Serial Number on NX-OS devices"
  robot_file: "catalog/NX-OS/verify_nxos_module_serial_number.robot"
  git_url: "https://wwwin-github.cisco.com/Testing-as-Code/tac-catalog"
  git_commit_sha: "feat/nx-os/add-verify-nxos-module-serial-number"

Changes

• New file: github_ops_manager/utils/cxtm.py - cxtm.yaml parsing utilities
• schemas/tac.py: Added CXTMTestCase, CXTMTestCaseGroup, CXTMConfiguration models
• configuration/cli.py: Added --cxtm-file option to process-test-requirements
• synchronize/test_requirements.py: Integrated cxtm.yaml lookup when rendering issue bodies
• templates/tac_issues_body.j2: Added "Test Case Definition" section

Usage

github-ops-manager repo ... process-test-requirements ./test_cases \
  --base-directory ./workspace/jobfiles \
  --cxtm-file ./cxtm.yaml

Pipeline Integration

The Google project Jenkinsfile has been updated to:

1. Run tac-tools synchronizer expand BEFORE process-test-requirements (so cxtm.yaml is populated)
2. Pass --cxtm-file ./cxtm.yaml to the command

Test plan

• Run unit tests (uv run pytest tests/unit/)
• Test with Google project pipeline
• Verify issue bodies contain test case definitions
• Verify tac-agent-worker can parse the new issue format

🤖 Generated with Claude Code