feat: discover environments from remote deployment repos

[hisco]

Summary

• Services with deploymentRepo now discover their environments from the remote deployment repo (clone → list overlays/ dirs → read skyhook/environments/{name}.yaml) instead of requiring a local environments[] array
• Services without deploymentRepo continue using local environments as before
• Token handling tries explicit github-token input first, falls back to GITHUB_TOKEN env var, with retry across tokens on auth failure
• Branch defaults to remote HEAD when not explicitly specified (instead of hardcoded main)
• autoDeploy added to the environment schema (defaults to false)
• README rewritten to document both Skyhook and Koala configuration formats

Environment schema change

autoDeploy is now part of the environment configuration, both in local skyhook.yaml and remote skyhook/environments/{name}.yaml files. It controls the auto_deploy field in the matrix output. Defaults to false when not specified.

Local (skyhook.yaml):

environments:
  - name: dev
    clusterName: nonprod-cluster
    autoDeploy: true       # new field, optional, default false
  - name: staging
    clusterName: nonprod-cluster
                            # autoDeploy omitted → "false"

Remote (skyhook/environments/dev.yaml):

clusterName: nonprod-cluster
cloudProvider: gcp
account: my-project
location: us-east1
namespace: dev
autoDeploy: true

Previously auto_deploy was hardcoded to "true" for all matrix entries.

Key changes

File	Change
src/deployment/repo-fetcher.js	New — shallow clone with caching (repo:branch), overlay listing, env config reading with cache (repo:branch:envName)
src/index.js	Wire up remote env resolution per service, token fallback via resolveTokens(), branch defaults to empty
src/matrix/matrix-builder.js	Accept perServiceEnvs map; read autoDeploy from env instead of hardcoding
src/config/SkyhookConfig.js	Add autoDeploy to SkyhookEnvironment (accepts bool/string, defaults false)
action.yml	Remove hardcoded main default for branch input
tests/skyhook.test.js	37 tests (19 new) covering clone caching, token fallback, overlay listing, env config parsing/caching, per-service envs, autoDeploy in both paths
README.md	Full rewrite documenting Skyhook remote env discovery, config formats, matrix output schema

Test plan

• All 37 tests pass (npm test)
• Token fallback: first token fails → retries with second token
• All tokens fail → throws with clear error
• Clone cache: same repo:branch cloned once, shared across services
• Env config cache: namespaced by repo:branch:envName, no cross-repo collisions
• Mixed services: remote-env service + local-env service produce correct matrix
• Environment filter applies to both remote and local envs
• No branch specified → git clone omits --branch (uses HEAD)
• autoDeploy: true/false/"true"/undefined all handled correctly in constructor
• autoDeploy: local path — matrix entries reflect env setting
• autoDeploy: remote path — read from YAML, defaults false when missing
• E2E: test in a workflow with a real deployment repo reference