fix(suggest): render a pure-deletion suggestion as a deletion, not an empty box

[adnaan]

prereview suggest has always accepted a suggestion whose proposed is empty — suggest_cmd.go:139-142 validates only file and from_line. But the card rendered the after-pane unconditionally, so a pure deletion painted an empty green box, which reads as a bug rather than as "this text goes away".

The before-pane was already conditional, for the mirror case of a pure insertion. This makes the after-pane conditional too, and adds the affordance that was missing:

• .sg-diff gains is-deletion, which strikes the before-pane through
• a .sg-del-note caption (delete — accepting removes L4) stands in for the absent green box, so the card still says what accepting will do

Why this is load-bearing rather than cosmetic

Deletions are the common case for a document-simplify workflow — a pass over a plan is mostly cuts. A tool that proposes cuts through prereview suggest is unusable while every cut renders as an empty box.

Rendering safety

Every non-deletion suggestion renders byte-identically:

• the 18 render goldens (TestTemplateRenderGolden) pass untouched
• only testdata/prereview.tmpl.sig.golden moves — an intentional content change, regenerated with -update-sig per the repo's template guard convention

Tests

e2e/e2e_deletion_suggestion_test.go (chromedp) asserts:

• no .sg-new element is emitted at all for a deletion — this is the actual regression; previously one existed and was empty
• the .sg-diff.is-deletion marker is present
• the before-pane still carries the removed text
• the caption is non-empty and says what will happen (an empty caption would reproduce the bug in a new element)
• accept/reject still work on a deletion
• an ordinary replacement card is completely unaffected

Verified failing against the pre-fix template before landing — reverting partials.tmpl to HEAD produces exactly the two intended failures, so the test goes red if this regresses.

Full unit suite green; full browser e2e suite green (573s). Confirmed by eye in a running prereview, not only by reading the template.

🤖 Generated with Claude Code

https://claude.ai/code/session_014g9DCfyYjDZsMQ4xocgCMj