feat: keep image-heavy sessions within provider request-size limits (#1508)

* feat(kosong): classify HTTP 413 request-body-too-large as a dedicated error type

* feat(agent-core): lower default image downscale cap to 2000px and make it configurable

* feat(agent-core): strip media to text markers and retry when the compaction request is too large

* feat(agent-core): cap model-initiated image reads with a configurable byte budget

* feat(agent-core): resend with degraded media when the provider rejects the request body as too large

* test(agent-core): add explicit timeouts to encode-heavy image budget tests

* feat: add WebP decoding support with wasm integration

- Introduced a new WebP decoding module using @jsquash/webp's wasm decoder.
- Implemented functions to decode WebP images and check for animated WebP formats.
- Updated image compression tests to include scenarios for WebP handling, including encoding and decoding.
- Enhanced error handling for API request size limits to accommodate various error messages.
- Updated pnpm lockfile to include new dependencies for WebP encoding and decoding.

* chore(changeset): consolidate this PR's entries into one

* fix(nix): update pnpmDeps hash for merged lockfile

* feat(agent-core): refuse HEIC/HEIF reads with platform-matched conversion guidance

apps/kimi-code/test/tui/controllers/editor-keyboard-image-paste.test.ts

@@ -141,14 +141,14 @@ describe('clipboard image paste compression', () => {
     if (att?.kind !== 'image') throw new Error('expected image attachment');
 
     // Stored metadata reflects the compressed size.
-    expect(Math.max(att.width, att.height)).toBeLessThanOrEqual(3000);
-    expect(att.placeholder).toContain('3000×1500');
+    expect(Math.max(att.width, att.height)).toBeLessThanOrEqual(2000);
+    expect(att.placeholder).toContain('2000×1000');
 
     // The stored bytes decode to the compressed dimensions — the thumbnail and
     // the submitted image both read from these bytes, so they cannot diverge.
     const dims = parseImageMeta(att.bytes);
     expect(dims).not.toBeNull();
-    expect(Math.max(dims!.width, dims!.height)).toBeLessThanOrEqual(3000);
+    expect(Math.max(dims!.width, dims!.height)).toBeLessThanOrEqual(2000);
   });
 
   it('records and persists the pre-compression original for an oversized paste', async () => {