fix(hooks): skip background task notification retrieval

[xiehuanyi]

The prompt hook now skips leading <task-notification> completion notices before running graft ask, injecting retrieval guidance or updating the session query. Human prompts that mention the tag later still use normal retrieval.

Fixes #500.

Validation: both plain and whitespace-prefixed notification regressions fail before the guard and pass after it; a human-query control still records the query. All 36 hook tests pass, the full suite reports 1,359 passed / 1 existing skip, and npm run build plus git diff --check pass. Tests exercise the actual hook entry point and retrieval subprocess boundary with the existing offline test seam.

AI-assisted implementation and wording.

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[trailhq-graft]

🌱 graft blast radius

Nothing outside this diff depends on it. 1 area changed; no indexed dependents at depth 2.
Tests: no test reaches Claude Hooks.
Tag: @anirudhkumar-nanonets — Claude Hooks · @shhdwi — Claude Hooks

Who knows this code — 2 people across 1 area

Area	Who knows it
Claude Hooks · changed	@anirudhkumar-nanonets — 10 commits, last 7d ago · @shhdwi — 10 commits, last 2mo ago

Ownership is git history over each area's own files, weighted towards recent work (120-day half-life). Merge commits and bots are dropped, and you are dropped from your own PR. A name with no @ has no GitHub handle in its commit email — tag them by hand, or add a .mailmap entry. A suggestion from history, not a CODEOWNERS rule.

Test signal per changed area — 1 ✗

Reached = a node under a test path has a resolved edge into the changed symbol. It undercounts anything called indirectly — through a CLI, a spawned process or a dynamic import — so read a low ratio as “look here”, never as a coverage gate.

• ✗ Claude Hooks — 0 of 1 reached · no test file reaches it
  • not reached: main

_{graft blast · origin/main...HEAD · depth 2 · 2 changed files}

Open the interactive graph → — click an area to see its dependent symbols at file:line.