skills(running-tend): scope data-loss review hold to the diff, not the file

[worktrunk-bot]

Refines the data-loss-surface review hold so it keys on what the diff touches, not on unrelated contents of the same file.

In #3453 I held a creation-only change to plugins/worktrunk/hooks/hooks.json purely because that file also ships the WorktreeRemove hook (wt remove), even though the diff never touched the removal path. @max-sixty flagged that as overly conservative:

just as a process point, this is overly conservative, @worktrunk-bot you should be deciding based on whether the code actually touches code that is in data-destruction paths, not whether there are unrelated changes in the file; please fix the guidance here

The old "edits a file that already contains one" trigger fired on mere co-location. This adds a "Scope the hold to the diff, not the file" subsection that splits the two cases the trigger was conflating:

• Source code (src/git/remove.rs) — still hold on proximity, because an edit near the force-delete path can change its behavior at a distance without the destructive line appearing in the diff. That rationale (the original "Both directions matter" note) is preserved.
• Structured config with independent entries (hooks.json's separate hook objects, alias tables) — hold only when the diff touches the destructive entry itself. Editing the WorktreeCreate command can't change what the separate WorktreeRemove hook does, so an edit confined to a non-destructive entry no longer warrants a hold.

The distinction is whether an edit can reach a destruction path structurally, which is exactly the "does the code actually touch a data-destruction path" test.

Separate PR from the code change it came out of, per the skill-overlay convention. Triggered from #3453 (comment).

[max-sixty]

cut verbosity of change by 70%, rewrite existing docs rather than patching

[worktrunk-bot]

Done — force-pushed a rewrite. Instead of adding a new subsection, I rewrote the existing "Both directions matter" paragraph in place; the change is now +9/−4 (net +5 lines) versus the previous +20. Both the source-proximity and structured-config cases are kept, just folded into one paragraph.

[max-sixty]

still too verbose; this is not a super complex thing, it doesn't need examples. Thank you

[worktrunk-bot]

Trimmed to four lines, no examples — just the source-proximity vs. structured-entry rule.