Resolve #2293: Separate Discord shutdown cleanup diagnostics

[ayden94]

Summary

• Closes [audit][area:infra-messaging] Separate Discord shutdown cleanup failures from initialization failures (P2) #2293.
• Distinguishes Discord bootstrap initialization failures from shutdown cleanup failures while preserving the public lifecycle state union.
• Adds status/service regression coverage and documents the diagnostics contract in EN/KO README files.
• Adds a patch changeset for the public @fluojs/discord diagnostics behavior change.

Testing

• pnpm exec biome check packages/discord/src/service.ts packages/discord/src/status.ts packages/discord/src/module.test.ts packages/discord/src/status.test.ts packages/discord/src/public-surface.test.ts packages/discord/README.md packages/discord/README.ko.md .changeset/clever-discord-cleanup-diagnostics.md
• pnpm --filter @fluojs/discord test
• pnpm --filter @fluojs/discord typecheck
• pnpm --filter @fluojs/discord build
• pnpm --filter @fluojs/discord... build
• pnpm verify:release-readiness
• GIT_MASTER=1 git diff --check

Notes

• This PR salvages the implementation worktree after issue-to-pr workers timed out before opening a PR.
• No worktree cleanup, branch deletion, issue close, or merge was performed by the worker.