feat: add durable goal loop

[woai3c]

Summary

Adds a durable /goal loop engineering implementation for x-code-cli. Goals are session-scoped, persisted, resumable, interruptible, and can complete only through verifier evidence or explicit user confirmation.

What changed

• Added core goal state, input queue, coordinator, runner, continuation prompts, final summaries, and durable session persistence.
• Added getGoal / updateGoal tools and CLI commands for create, status, pause, resume, cancel, clear, edit, steer, and verify.
• Added shell, file, sub-agent, and user-confirmation verifier paths.
• Stops each inner agent loop immediately after a goal transition so the host runner controls retries and terminal state.
• Blocks no-verifier and unsafe sub-agent verifier configurations instead of looping indefinitely.
• Enforces token budgets after each outer turn and reports remaining budget in /goal status.
• Uses semantic blocker matching so equivalent blocker reports converge after three outer turns.
• Keeps slash control commands usable while permission and selection dialogs are open.
• Preserves /clear history behavior while clearing the current viewport.
• Fixes long Markdown/tool-output rendering so bottom table borders are retained.
• Adds a root Vitest alias for @x-code-cli/core, so pnpm test works in a clean checkout without prebuilt core dist.

Risk areas reviewed

• Goal transitions cannot trigger repeated updateGoal calls inside one agent turn.
• Goal creation is rejected while a non-terminal goal exists.
• Resume, pause, cancel, and clear drain pending interactive requests.
• Missing or non-retryable verifiers terminate as blocked.
• Shell verifiers receive the shared abort signal and pass through permission checks.
• Sub-agent verifiers cannot recurse and destructive verification prompts are rejected.
• Long content commits reserve terminal frame rows before repainting.
• Test resolution no longer depends on generated artifacts left by a prior build.

Verification

• pnpm run ci
• pnpm format:check
• Clean-dist pnpm test: 73 files, 822 passed, 4 skipped
• Targeted clean-dist CI regression suites: 12 passed
• Manual checklist and terminal/debug logs reviewed, including verifier retry, blocker convergence, /clear, and long-table rendering

Manual testing

The checklist is at tmp/goal-loop-manual-test-plan.md.