fix(hooks): wire unverified-tag-ledger into settings and declare its subagent opt-out

[EdbertChan]

CI caught the hook shipping unwired. Two repo gates failed on it:

FAIL: test_every_claude_hook_entrypoint_is_in_settings
AssertionError: Lists differ: ['unverified-tag-ledger/claude_prompt_reminder.py'] != []

FAIL: test_every_stop_hook_is_mirrored_or_opted_out_with_reason
(hook='unverified-tag-ledger', command='.../claude_stop_check.py')

The hook directory had both fragments but no install_claude_hook.py, install.sh
never called one, and claude.hook.json declared no subagent_stop stance -- so
the Stop and UserPromptSubmit entries never reached ~/.claude/settings.json.

Adds the installer on diu-stop's pattern (same idempotent per-hook-type merge,
since this hook also owns one Stop and one UserPromptSubmit fragment), calls it
from install.sh next to diu-stop's, and opts the Stop hook out of subagent
mirroring with a reason: the ledger is keyed by session id, so a subagent would
log its tags against the parent's ledger, and a subagent has no next user
prompt to be reminded at.

Co-Authored-By: Claude Opus 5 (1M context) noreply@anthropic.com
Claude-Session: https://claude.ai/code/session_018u8S5ct3kFhosinSbybc7W

Depends-On: #468

---

Note

Low Risk
Install-time merge into local settings only; behavior follows an established hook installer pattern with no auth or data-path changes.

Overview
Fixes CI failures where unverified-tag-ledger had hook fragments and scripts but never reached ~/.claude/settings.json.

Adds install_claude_hook.py (same idempotent, marker-based merge as diu-stop) for Stop (claude_stop_check.py) and UserPromptSubmit (claude_prompt_reminder.py), and invokes it from install.sh in the Claude settings merge block.

Updates claude.hook.json with subagent_stop.inherit: false and a documented reason so the Stop hook is not mirrored to subagents (session-scoped ledger and no next user prompt for reminders).

^{Reviewed by Cursor Bugbot for commit 0fc2a13. Bugbot is set up for automated code reviews on this repo. Configure here.}

[EdbertChan]

This pull request is part of a Mergify stack:

#	Pull Request	Link
1	feat(hooks): log CAT-UNVERIFIED tags instead of treating them as evidence	#464
2	feat(hooks): refuse a CAT-UNVERIFIED tag from a turn that ran no check	#468
3	fix(hooks): wire unverified-tag-ledger into settings and declare its subagent opt-out	#474	👈

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