fix: support offline model catalog startup

[LeXwDeX]

Summary

• make models.dev catalog fetch failures non-fatal and publish a degraded-state event
• embed models.dev api.json during release packaging so single binaries start in air-gapped environments
• redirect TUI console output to the log file while the renderer owns the terminal, and show a safe warning toast for catalog fetch failures

Verification

• ./packages/sdk/js/script/build.ts
• bun typecheck (packages/core)
• bun typecheck (packages/opencode)
• bun typecheck (packages/tui)
• bun turbo typecheck (commit/push hook)
• bun test test/models-dev.test.ts test/plugin/models-dev.test.ts (packages/core)
• bun test test/provider/provider.test.ts (packages/opencode)
• bun test test/session/prompt.test.ts (packages/opencode)
• openspec validate fix-offline-startup
• release-fork.yml YAML parse
• source offline smoke: OPENCODE_MODELS_URL=http://127.0.0.1:9 + missing OPENCODE_MODELS_PATH debug command
• single build smoke with MODELS_DEV_API_JSON and generated binary --version
• generated binary offline smoke command

Notes

• Windows offline smoke was not run locally because this machine is macOS; the release workflow includes windows build coverage.
• OpenSpec planning files are under ignored openspec/ and are not included in this PR.