fix(hook): keep ask decision on claude rewrites

[YOMXXX]

Summary

• emit an explicit permissionDecision: "ask" for Claude native hook rewrites that are not explicitly allowed
• keep permissionDecision: "allow" limited to AllowRewrite, so mixed compounds with unallowed segments are not auto-approved
• add regression coverage for mixed compound rewrites and the default ask-not-allow path

Fixes #2549

Verification

• cargo +1.93.0 test claude_mixed_compound -- --nocapture
• cargo +1.93.0 test claude_default_rewrite_is_ask_not_allow -- --nocapture
• cargo +1.93.0 test claude_ -- --nocapture
• cargo +1.93.0 run --quiet -- hook claude with the reported mixed-compound stdin payload
• cargo +1.93.0 test hook_cmd -- --nocapture
• cargo +1.93.0 fmt --all -- --check
• cargo +1.93.0 clippy --all-targets
• cargo +1.93.0 test --all -- --skip small_grep_not_worse_than_plain
• git diff --check