feat(migrate): add migrate command with GitHub Actions and Bamboo support

[Viktor (tiulpin)]

First in a series splitting up #217. Foundation + GitHub Actions + Bamboo converters. Rebased onto main now that the shared pipelineschema/schema-cache refactor (#370) and the migrate issue template (#371) have merged.

What's in

• teamcity migrate: detect → convert → validate → write .tc.yml
• GitHub Actions: actionlint-based, ~60 action transformers
• Bamboo Specs: stage flattening, ~30 task transformers, ${bamboo.*} → %param%
• Builds on the shared internal/pipelineschema + cmdutil.FetchOrCachePipelineSchema (refactor(pipeline): extract pipelineschema package and shared schema cache #370)
• skills/migrate-to-teamcity/ covers GHA + Bamboo (mappings, gotchas, schema)
• FUS telemetry: emits teamcity.cli.migrate.completed (source / outcome / validation_status / is_dry_run) and adds migrate to the command enum. (The fus-reporting-api-go bump for the anonymized-field regexp#hash fix landed in refactor(pipeline): extract pipelineschema package and shared schema cache #370.) Metadata registration tracked in FUS-8018.
• Addresses all 8 findings from the 55-repo validation report (schema-valid runs-on derived from the server schema, matrix/expression runners no longer dropped, reusable-workflow with:/secrets: preserved, Bamboo !include + nested spec detection, consistent exit codes)

Output uses ✓ / ⚠ / ✗ per file. Each future CI adds one <ci>.go + fixture + switch case.

Follow-ups

GitLab → Jenkins → CircleCI → Azure → Bitbucket → Travis. Reference branch: #217.

QA

Binaries: https://cli.teamcity.com/pipeline/CLI_CiCd/10884?job=10887&focusLine=1&logView=linear&tab=artifacts&pipelineRunTab=pipeline

# extract the right archive for your OS, then:
./teamcity migrate --help

GitHub Actions:

cd <any repo with .github/workflows/*.yml>
./teamcity migrate --dry-run
./teamcity migrate                # writes <name>.tc.yml next to source
./teamcity pipeline validate <name>.tc.yml

Bamboo:

cd <any repo with bamboo-specs/*.yml or bamboo.yml>
./teamcity migrate --dry-run
./teamcity migrate
./teamcity pipeline validate <name>.tc.yml

Filter to one source: --from github-actions or --from bamboo. JSON output: --json.

Check that Manual setup needed: lists triggers / secrets / branch filters / (Bamboo) final-tasks / manual stages — those are intentionally not auto-converted.

Skill

migrate-to-teamcity ships in the binary; install for your AI agent (Claude Code / Cursor / etc.):

./teamcity skill list                      # confirm migrate-to-teamcity is bundled
./teamcity skill install migrate-to-teamcity --project
# or globally:
./teamcity skill install migrate-to-teamcity

Then in the agent, ask it to migrate a repo (e.g. "migrate this Bamboo project to TeamCity"). It should pull the skill, run teamcity migrate, fix stubs from mappings.md, and surface manual-setup items from gotchas.md. Remove with ./teamcity skill remove migrate-to-teamcity.

Test plan

• go test ./...
• golangci-lint run
• teamcity migrate --dry-run on GHA fixture
• teamcity migrate --dry-run on Bamboo fixture
• Dogfooded on a real repo