feat: delete a decision, manage assets while writing, and sweep before deploying

Four things an author could not do, and the check that should have caught them.

A Decision could not be deleted. Case, Reference and Question all could, so an
author who opened a decision draft had no way to close it. The contract gained
the operation and the list now offers it for every kind. Its path carries the
project because a decision belongs to one; a row with no project says so rather
than failing.

Assets could only be managed by leaving the document. The picker now deletes
one in place — the server still refuses an asset a document uses — so a
mistaken upload does not cost the author their editing session.

Zoom was decided for the author and could not be changed: only a DIAGRAM got
it, so a screenshot uploaded as an image or attachment went in with zoom off
and no way to turn it on. It now defaults on for images and the picker offers
the choice. The toggle is a picker control, not a document field, and carries
its own class — wearing the field class put it in the editor's field list.

`scripts/smoke/production-sweep.ts` walks every public and Studio screen and
the document flow, reporting console errors, failed API calls and error text.
It exists because verifying only the screen I had just changed is what let
broken screens reach production repeatedly; this runs before a deploy, not
after a report.

src/features/tech-log/presentation/styles/studio-editor.css

@@ -86,6 +86,10 @@
    a flex container both default to an automatic minimum of their min-content
    size, so at 360px the search row sized itself to 366px inside a 328px column
    and pushed the submit button off-screen (document scrollWidth 382). */
+/* Picker 자체의 옵션이지 문서의 입력 칸이 아니다 — `studio-field` 를 쓰면 편집기의 칸 목록에
+   섞여 들어간다. 모양은 그 칸들과 같게 두고 이름만 분리한다. */
+.studio-app .asset-picker-option { display: flex; align-items: center; gap: 10px; margin-bottom: 14px; color: var(--muted); font-size: 12px; font-weight: 650; }
+.studio-app .asset-picker-option input { width: 18px; min-width: 18px; min-height: 18px; padding: 0; }
 .studio-app .asset-picker-search { display: grid; grid-template-columns: minmax(0, 1fr); max-width: 420px; gap: 8px; margin-bottom: 14px; color: var(--muted); font-size: 12px; font-weight: 650; }
 .studio-app .asset-picker-search div { display: flex; min-width: 0; gap: 8px; }
 .studio-app .asset-picker-search input { min-width: 0; flex: 1; min-height: 44px; padding-inline: 12px; border: 1px solid var(--line-strong); border-radius: 5px; background: var(--paper); color: var(--ink); font-size: 14px; }