id(web/editor): image parseDOM bare Number() lets NaN/fraction/hex dimensions through — pasted image sizing silently lost or reinterpreted on save #2010

Problem

In the id web editor, the image node's parseDOM converts the width/height attributes with a bare Number() and the attrs declare no validation, so non-integer dimensions are stored verbatim and then silently dropped (or reinterpreted) downstream:

• pkgs/id/web/src/editor.ts:145-146 — width: el.getAttribute("width") ? Number(el.getAttribute("width")) : null (same for height). The image attrs at editor.ts:125-126 are { default: null } with no validate, unlike ordered_list's order which at least declares validate: "number" (and still lets NaN through — id(web/editor): ordered_list parseDOM bare Number() lets NaN/fractional start through — pasted lists silently renumber from 1 on save #2005).
• pkgs/id/web/src/editor.ts:157-158 — toDOM emits the attr only if (node.attrs.width): NaN and 0 are falsy, so they vanish; a fraction (2.5) or negative (-5) is emitted as the invalid attribute width="2.5" / width="-5".
• pkgs/id/src/web/markdown.rs:1953-1954 — on save, json["attrs"]["width"].as_u64() is None for a fraction, a negative, and for NaN (which serialises to JSON null), so the dimension is dropped from the saved markdown with no error. The Rust-side HTML parse (markdown.rs:1208-1215) accepts only a pure u64, so the editor is the permissive side of an asymmetric pair.
• pkgs/id/web/src/image-node-view.ts:58-62 — the node view sets img.style.width = ${width}px``; NaNpx / `-5px` are invalid and silently ignored by the browser.

Verified this run (2026-10-28, main 38f1f00f)

Probe on the laptop (~/git/fleet/probe-2026-10-28-laneB-imgdim/, the shipped getAttrs conversion copied verbatim; editor.ts sha256 4340aef4… identical on laptop and sandbox main), with the toDOM truthiness check and the save-side as_u64() semantics modelled from the shipped code:

• Control width="200" → parseDOM 200, toDOM "200", saved 200 ✓
• width="200px" → NaN → toDOM omits the attribute, saved null — dimension silently lost
• width="50%" → NaN → same silent loss
• width="2.5" → 2.5 → toDOM emits width="2.5", saved null — lost on save
• width="-5" → -5 → toDOM emits width="-5", saved null — lost on save
• width="abc" → NaN → silently lost
• width="0x10" → 16 and width="1e3" → 1000 — silently reinterpreted as values the author never wrote (an HTML dimension attribute is a leading-digits value, not a JS numeric literal)

Pasted web content is the realistic source: images in copied HTML routinely carry width="200px", percentage widths, or fractional/negative junk from CMS markup, and every one of those pastes loses its sizing on the next save without any signal.

Why it matters

This is the same silent-coercion class as #2005 (ordered-list start) in the adjacent node of the same file, but with a different failure shape: the list renumbers, the image loses its dimensions (or gains ones nobody typed, 0x10 → 16). The repo's own strict parsers show the intended pattern — parseWorldSeed (web/src/world-seed.ts, #707/#832) accepts only decimal digits, and parseProxyPortValue does the same for the bin proxies (#483). The image attrs are an unhardened spot the earlier passes missed.

Acceptance criteria

• Image width/height from parseDOM are either a non-negative integer or null: a value that is not a plain run of decimal digits (e.g. 200px, 50%, 2.5, -5, abc, 0x10, 1e3) never reaches the node attrs as NaN, a fraction, a negative, or a reinterpreted number — it is dropped to null at parse time (the triage-pinned contract may instead take the HTML leading-digits value, but it must be one documented behaviour, applied identically to width and height).
• The editor-side result agrees with the save side: any dimension the editor keeps survives markdown.rs's as_u64() round-trip, and any it drops is dropped at parse time, not discovered missing after save.
• Regression tests (web/src/editor.test.ts or a sibling) cover at least: "200" (kept), "200px", "50%", "2.5", "-5", "0x10" — asserting the resulting attrs; existing editor tests still pass.
• The fix is scoped to the image node (the ordered-list site is id(web/editor): ordered_list parseDOM bare Number() lets NaN/fractional start through — pasted lists silently renumber from 1 on save #2005's, already filed).

Filed by new-issue-creator-code-b. Related: #2005 (same file, same bare-Number() class, ordered_list node), #893 (image parseDOM link handling).