feat(ux): surface goal lifecycle state

[willytop8]

Summary

• add explicit active, paused, and blocked state plus completion-audit
  disclosure to goal status/list output
• emit bounded, transition-only lifecycle notices through OpenCode logging and
  TUI toast surfaces, with independent public opt-out/custom-sink options
• harden terminal rollback, blocked-ledger recovery, and clear durability around
  concurrent session changes
• document the new UX and preserve the existing Active goal: compatibility
  heading

Why

Issue #49 correctly identifies that a deliberate pause or safety stop can look
like a random loop exit when users do not immediately see state and reason. The
plugin already had authoritative state and history; this change exposes that
state without adding model turns or making notification delivery part of the
correctness path.

The persistent internal Todo UI, interactive argument picker, and permanent
native Goal panel remain separate host-dependent enhancements. This PR does not
claim those surfaces.

Closes #49.

Verification

• npm test — 350/350 passed
• npm run release:check — passed
• coverage — 98.38% lines, 90.55% branches, 90.51% functions
• mutation contract — 67/67 critical mutants killed
• behavior benchmark — 100/100
• packed host/tool contracts, installer verification, production audit, and
  package-content check — passed
• real OpenCode 1.18.11 canary using the exact packed candidate — passed create,
  active status, pause, paused status, resume, edit, final status, default host
  logging, notice privacy, and process cleanup with an isolated localhost
  provider

Release impact

This introduces the public lifecycleMessages and lifecycleMessenger
options, so the follow-up release should be 0.7.0 under the documented
compatibility policy.