fix(cli): survive unavailable chat log directory

[c8dhjp4tyv-bit]

Recreated on the rewritten main after #1099 was auto-closed during repository maintenance. This carries the same reviewed change set on the new history.

Summary

• prevent logger initialization from crashing the CLI when the current chat directory cannot be created
• keep file logging best-effort while preserving the existing development and production destinations
• add regression coverage for both destinations and the unavailable-chat-directory path

Fixes #783

Validation

Prior validation before the history rewrite:

• logger.test.ts: 3 passed
• common typecheck: passed
• SDK typecheck: passed
• git diff --check: passed
• full CLI test command: 2,111 passed; existing checkout/environment failures remain in unrelated Infisical, read-only config, and missing release-dependency tests

[codebuff-team]

Good instinct and clean execution. Extracting resolveLogTarget as a pure, injectable function (cli/src/utils/logger.ts) makes the dev/production branching testable without touching the filesystem, and wrapping both directory resolution and setLogPath in try/catch in trySetLogPath correctly turns a hard crash into best-effort logging, which matches the intent of #783.

The three logger.test.ts cases cover the two normal destinations plus the failure path, and the assertions (currentChatDirCalls stays 0 in dev, target is undefined when getCurrentChatDir throws) are meaningful rather than tautological.

A couple of things worth double-checking before porting:

• Confirm CHAT_LOG_FILENAME is already exported from logger.ts (not shown as changed in this diff) since the test imports it directly.
• Swallowing the error silently in trySetLogPath means there's no signal at all (not even a stderr warning) that file logging failed — worth considering whether a single best-effort console.error on the caught error would help debugging without reintroducing the crash risk. Not blocking, but a reasonable follow-up.

Small, in-scope, focused change with regression coverage — good candidate for porting as-is.

[c8dhjp4tyv-bit]

Confirmed CHAT_LOG_FILENAME is already exported (export const CHAT_LOG_FILENAME = 'log.jsonl'). I kept the startup fallback silent intentionally rather than adding console.error: stderr output during startup can corrupt the interactive terminal UI, while file logging is explicitly best-effort. Added that rationale to the catch-path comment. Logger regression tests: 3 passed, 0 failed.