Fix lifecycle updates failing after acceptance and activation #2051

Summary

The latest end-to-end planning run successfully performed acceptance and activation side effects, but each workflow concluded as failed when the final lifecycle-state update was rejected by the deterministic validator.

This is a false-failure product defect: work is created successfully while the canonical lifecycle tracker remains stale and GitHub reports a failed run.

User impact

• Successful acceptance or activation appears broken.
• The lifecycle tracker can remain at an earlier state instead of Activated.
• Users may retry because the run is red, increasing concern about duplicate epics/tasks.
• Failure-report issues are generated for operations whose primary side effects succeeded.
• Demos and downstream automation cannot rely on workflow conclusion or lifecycle state.

Evidence

• Upstream E2E tracking: Pilot automatic Squad casting, onboarding, and research #2009
• E2E origin: https://github.com/octodemo/eshop-bradyg-dev/issues/4
• Acceptance run: https://github.com/octodemo/eshop-bradyg-dev/actions/runs/34986842391
• Activation run: https://github.com/octodemo/eshop-bradyg-dev/actions/runs/34987615314
• Prior validation change: Fix failed validation lifecycle retry output #2046
• Unresolved review identifying producer/validator mismatch: https://github.com/bradygaster/squad/pull/2046#discussion_r4013523240

The failing runs report that the lifecycle body must contain an H2 lifecycle heading, state, last-command, and a nonterminal next-action consisting of a backticked /squad command. The shared validator now applies to every planning mode, while canonical lifecycle-producing guidance can still emit command-plus-prose. Terminal recognition must also correctly handle the actual /squad plan activate path.

Scope

Keep the correction focused on the existing lifecycle contract:

• Align lifecycle-producing instructions/templates with the deterministic validator.
• Require command-only Next action values for nonterminal lifecycle states, with explanatory prose outside that field.
• Correctly classify /squad plan activate and the resulting Activated state as terminal.
• Update the shared planning ontology rather than patching only one validation branch.
• Add realistic regression coverage for scope acceptance, implementation acceptance, activation, and terminal activated state.

Acceptance criteria

• Acceptance completes with a green workflow conclusion and updates the canonical lifecycle tracker.
• Activation completes with a green workflow conclusion and records Activated.
• A successful activation does not create a failure-report issue.
• Retrying the corrected path does not duplicate generated epics or tasks.
• Prompt/contract tests include realistic lifecycle bodies from the affected phases.
• Existing lifecycle heading, state, last-command, metadata, and trust checks remain enforced.
• npm run build and the smallest relevant gh-aw reliability/contract tests pass.

Out of scope

• Redesigning the planning lifecycle or adding commands.
• Changes to generated application work in the E2E consumer repository.
• Unrelated stale template-copy cleanup tracked by bug: squad upgrade leaves .squad/templates skills and workflows stale #2047/enhancement: drop template folder from .squad #1436.
• Release versioning or package publication; those follow after this fix is verified.