[feat] Validate workflows, prompts and scorers in review --branch #1248

Parent: #818

Goal

Let a team repo stop a broken workflow before it merges. teamai review --branch <name> already exits 1 on a fail finding "so CI can gate on it" (src/review-branch.ts:506-509, :541), but it checks only skills, rules and agents (:108-115). A branch with an invalid workflow passes it, and push only warns (src/push.ts:869-877). Today the error shows up at the next pull, which keeps the last valid version.

Example

team-repo PR adds workflows/deploy.yaml with  needs: [biuld]

CI: teamai review --branch feature/deploy
  fail  workflows/deploy.yaml  step "release" needs "biuld", which is not a step in this workflow
  exit 1  → merge blocked

Scope

• review --branch validates workflows/ with the validator pull uses (syncWorkflowDefinitions, which already returns diagnostics in invalid), including the prompt_file targets under prompts/ (src/workflow/cache.ts:420-458). Each invalid file is a fail finding with its path and message.
• When [feat] Add workflow scorers and recorded quality labels #1085 adds scorers/, its validator joins the same check.
• The guide shows the CI job.

Out of scope

Changing push, and checking that a workflow runs.

Dependencies

• Blocked by: none
• Unblocks: none

Acceptance criteria

• The example branch fails review --branch with the finding shown, and exit code 1.
• A branch whose workflows all validate passes, and the check writes nothing.

Verification

Focused review-branch tests with a valid and an invalid workflow; build/typecheck/lint; one real-CLI run of review --branch on a fixture team repo. Bilingual guide update.