feat(cli): add custom session id startup flag

[tt-a1i]

Summary

Fixes #820.

Adds a new --session-id <id> startup flag for callers that want a stable session id:

• resumes the matching session when it already exists in the current workdir
• creates a new session with that id when it does not exist
• keeps --session resume-only
• rejects ids that already exist under another workdir and prints a cd hint
• supports the hidden --session_id alias for compatibility with the issue request

Also updates EN/ZH docs, CLI validation, tests, and the changeset.

Validation

• pnpm --filter @moonshot-ai/kimi-code exec vitest run test/cli/options.test.ts test/cli/session-flag-picker.test.ts test/cli/run-prompt.test.ts test/tui/kimi-tui-startup.test.ts
• pnpm --filter @moonshot-ai/kimi-code exec vitest run
• pnpm --filter @moonshot-ai/kimi-code run typecheck
• pnpm exec oxlint --type-aware apps/kimi-code/src/cli/commands.ts apps/kimi-code/src/cli/options.ts apps/kimi-code/src/cli/run-prompt.ts apps/kimi-code/src/main.ts apps/kimi-code/src/tui/kimi-tui.ts apps/kimi-code/src/tui/types.ts apps/kimi-code/test/cli/options.test.ts apps/kimi-code/test/cli/run-prompt.test.ts apps/kimi-code/test/cli/session-flag-picker.test.ts apps/kimi-code/test/tui/kimi-tui-startup.test.ts --quiet
• pnpm --filter @moonshot-ai/kimi-code run build
• git diff --check

Checklist

• Tests updated
• Docs updated
• Changeset added

AI Assistance Disclosure

I used Codex to review the changes, sanity-check the implementation against existing patterns, and help spot potential edge cases.

[changeset-bot]

🦋 Changeset detected

Latest commit: 927ec4b

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@moonshot-ai/kimi-code	Minor

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Preserve custom session IDs after OAuth login

When kimi --session-id foo is started with a missing or expired OAuth login, this initial createSession call can throw isOAuthLoginRequiredError and init() enters the login-required state. After the user completes /login, AuthFlowController.activateModelAfterLogin() creates the session without passing startup.sessionIdFlag, so the eventual session gets a generated id instead of the user-specified foo. This breaks the create-with-stable-id path specifically for first-time/expired-login startup; carry the pending custom id into the post-login create path.

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