fix(prompt-hook): skip Claude Code <agent-message> subagent hand-backs (#2184)

[danusha2345]

Fixes #2184

Claude Code hands a subagent's report back to the parent session as a UserPromptSubmit prompt wrapped in <agent-message from="…">…</agent-message>. The prompt hook treated it as user input and ran a full codegraph_explore on the whole report. That is slow on a multi-KB prose query — past Claude Code's 30 s hook timeout in the report — and when it does finish, the injected context is matched from words in the report, not from anything the user asked.

Change

• isAgentMessage(prompt) next to isTaskNotification (prompt-hook fires on Claude Code's system-injected <task-notification> messages: 3.5s median, 7.4s max on the blocking path #1832/fix(prompt-hook): skip Claude Code task notifications (#1832) #1884), same rule: only a prompt that is entirely the envelope is skipped, so a user question that quotes the tag still goes through the gate.
• codegraph prompt-hook returns before any project lookup when either matches.

Tests

• Unit cases for isAgentMessage (full envelope, surrounding whitespace, no attributes; a user question quoting it, trailing text, <agent-messages> and an unclosed envelope are not skipped).
• End-to-end: the hook injects context for a report that names indexed symbols, and prints nothing for the same report inside <agent-message>.
• These fail on main (the hook injects explore output for the envelope) and pass with the fix.

Measured

On a 375-file index, an 8 KB report took the hook 60 s on main; wrapped in <agent-message> it now exits in 0.17 s.

Not in this PR

Hook time grows faster than prompt length (500 chars → 2.3 s, 2 KB → 13 s, 4 KB → 40 s on that index): explore runs a separate search for every query term, with no cap on how many, re-reads SELECT DISTINCT name FROM nodes per term in the fuzzy/substring passes, and re-splits the whole query for every candidate path in scorePathRelevance. So a ~4 KB prose prompt typed by a user can still pass the 30 s timeout. Happy to follow up separately.

🤖 Generated with Claude Code

[colbymchenry]

Thank you! This landed in #2281: your commit carried onto current main with its authorship kept, plus a changelog credit.