Plan mode: auto mode classifier gives no verdict for the designated plan file when CLAUDE_CONFIG_DIR is set

Environment: Claude Code 2.1.278, WSL2 Ubuntu, auto mode enabled. Multi-account setup per docs: side instances use CLAUDE_CONFIG_DIR=~/.claude-<name>; their plans/ is a symlink to ~/.claude/plans.

Bug: In plan mode, Write to the harness-designated plan file ~/.claude-<name>/plans/<plan>.md fails with "The server-side auto mode classifier gave no verdict (it skipped this action), so auto mode cannot determine the safety of Write. Retrying this action will not change that." The file is never created, retries do not help, and ExitPlanMode consequently cannot present the plan. Plan mode is therefore broken in every instance with a custom CLAUDE_CONFIG_DIR; the default ~/.claude instance is unaffected.

Deterministic A/B repro (single session, same account, context, permissions; consecutive calls):

1. Write → ~/.claude-director/plans/<designated>.md → classifier gives no verdict, write refused.
2. Write → ~/.claude/plans/test.md → succeeds on the first try.

Both paths resolve to the same physical directory via the symlink, which rules out filesystem, permissions, ownership and content. The decision follows the literal path string: the classifier appears to recognize the plan-file location by the ~/.claude/plans/ pattern and does not account for CLAUDE_CONFIG_DIR.

Side finding: step 2 also shows plan mode allowed writing a file that is not the designated plan file, as long as the path matches the recognized pattern — the plan-mode single-file restriction seems to be enforced by directory pattern, not by the designated file.

Timeline: identical CLI version (2.1.278 since Sep 19) and identical local config worked until the evening of Sep 21 (last success 21:55 CEST, first failure 21:21 CEST — transitional phase), deterministic failure since Sep 22. Points to a server-side classifier rollout. Writes to the same instance paths outside plan mode keep working the whole time.

Workaround: write the plan via the resolved path ~/.claude/plans/<name>.md (same file through the symlink; ExitPlanMode finds it), or transfer the plan via Bash cp.

Likely related: #95982 (same day, same version, "no verdict" for ordinary project-local writes — plausibly the same server-side regression with a different manifestation), #95370, #95996.