feat(core,studio,cli): add square + square-4k canvas resolutions

The four existing presets only cover 16:9 (landscape) and 9:16 (portrait)
aspect ratios. A 1080×1080 square comp had nowhere to land at any scale:
"Auto" rendered at the comp's authored 1080×1080, and picking 1080p or 4K
mapped to a landscape/portrait preset whose aspect ratio mismatched, which
the producer's resolveDeviceScaleFactor validator rejects with
"does not match the aspect ratio of the composition".

Add `square` (1080×1080) and `square-4k` (2160×2160) to CANVAS_DIMENSIONS
in core. The existing `keyof typeof CANVAS_DIMENSIONS` derivation
extends the `CanvasResolution` union and `VALID_CANVAS_RESOLUTIONS` array
automatically, so the producer's validator, the render API route, and
the CLI `--resolution` flag pick the new presets up without further
changes.

- core: extend CANVAS_DIMENSIONS, RESOLUTION_ALIASES, and the
  htmlParser to recognize `data-resolution="square|square-4k"` and to
  infer square from equal width/height (vs. the prior "square defaults
  to portrait" tie-breaker).
- studio: extend the local ResolutionPreset / CANVAS_DIMENSIONS mirrors;
  collapse isPortraitComp into a 3-way `compAspect` helper so
  resolveResolution returns the square preset for square comps.
- cli: update --resolution help text on `init` and `render` to mention
  the new presets.
- tests: add square cases to renderOrchestrator's resolveDeviceScaleFactor
  suite (returns 1 for square→square, 2 for square→square-4k, rejects
  landscape preset on square comp), update the htmlParser test that
  previously pinned the "square→portrait" tiebreaker.

packages/cli/src/commands/init.ts

@@ -630,7 +630,7 @@ export default defineCommand({
     resolution: {
       type: "string",
       description:
-        "Canvas resolution preset: landscape (1920x1080), portrait (1080x1920), landscape-4k (3840x2160), portrait-4k (2160x3840). Aliases: 1080p, 4k, uhd. Default: keep template dimensions (typically 1920x1080).",
+        "Canvas resolution preset: landscape (1920x1080), portrait (1080x1920), landscape-4k (3840x2160), portrait-4k (2160x3840), square (1080x1080), square-4k (2160x2160). Aliases: 1080p, 4k, uhd. Default: keep template dimensions (typically 1920x1080).",
     },
   },
   async run({ args }) {
@@ -670,7 +670,7 @@ export default defineCommand({
         console.error(
           c.error(
             `Invalid --resolution: "${args.resolution}". ` +
-              `Use one of: landscape, portrait, landscape-4k, portrait-4k (or aliases 1080p, 4k, uhd).`,
+              `Use one of: landscape, portrait, landscape-4k, portrait-4k, square, square-4k (or aliases 1080p, 4k, uhd).`,
           ),
         );
         process.exit(1);

packages/cli/src/commands/render.ts

@@ -220,7 +220,7 @@ export default defineCommand({
     resolution: {
       type: "string",
       description:
-        "Output resolution preset: landscape (1920x1080), portrait (1080x1920), landscape-4k (3840x2160), portrait-4k (2160x3840). Aliases: 1080p, 4k, uhd. The composition is unchanged — Chrome renders at higher DPR (deviceScaleFactor) so the captured screenshot lands at the requested dimensions. Aspect ratio must match the composition; the scale must be an integer multiple. Not yet supported with --hdr.",
+        "Output resolution preset: landscape (1920x1080), portrait (1080x1920), landscape-4k (3840x2160), portrait-4k (2160x3840), square (1080x1080), square-4k (2160x2160). Aliases: 1080p, 4k, uhd. The composition is unchanged — Chrome renders at higher DPR (deviceScaleFactor) so the captured screenshot lands at the requested dimensions. Aspect ratio must match the composition; the scale must be an integer multiple. Not yet supported with --hdr.",
     },
   },
   async run({ args }) {
@@ -263,7 +263,7 @@ export default defineCommand({
       if (!outputResolution) {
         errorBox(
           "Invalid resolution",
-          `Got "${args.resolution}". Must be one of: landscape, portrait, landscape-4k, portrait-4k (or aliases 1080p, 4k, uhd).`,
+          `Got "${args.resolution}". Must be one of: landscape, portrait, landscape-4k, portrait-4k, square, square-4k (or aliases 1080p, 4k, uhd).`,
         );
         process.exit(1);
       }