fix: respect CLAUDE_CODE_DISABLE_TERMINAL_TITLE in UserPromptSubmit hook

[Saradhii]

Summary

• Respects the CLAUDE_CODE_DISABLE_TERMINAL_TITLE=1 environment variable in the UserPromptSubmit hook
• When set, omits the query field from the prompt_submit payload so Warp does not overwrite the user's custom tab title
• The notification still fires for session status transitions (idle → running), only the title text is suppressed
• Adds 3 new tests covering the behavior

Problem

Users who set CLAUDE_CODE_DISABLE_TERMINAL_TITLE=1 to opt out of terminal title updates still had their tab title overwritten by the plugin's UserPromptSubmit hook, because the env var was not checked before sending the prompt text to Warp.

Changes

• on-prompt-submit.sh: Check CLAUDE_CODE_DISABLE_TERMINAL_TITLE after extracting the query. If set to 1, clear the query and conditionally build the payload args so the query field is entirely omitted (not just empty string).
• test-hooks.sh: Add tests verifying query is present without the env var, query is absent with CLAUDE_CODE_DISABLE_TERMINAL_TITLE=1, and the event type is still prompt_submit.

Test plan

• All 42 tests pass (39 existing + 3 new)
• bash plugins/warp/tests/test-hooks.sh — 0 failures

Fixes #24