feat(web): whole-page image drop, projected intake limits, and thumbnail tiling

Second alignment step for #2248: document-level drag intake behind the new
DropOverlay atom, lightbox close icon and shared dialog mask, DeepSeek Chat
thumbnail rules (single 240px long edge with ratio clamp, 64px tiles, merged
consecutive assistant images), image limits raised to 20/10MiB/100MiB and
published to clients as the imageLimits projection, whole-batch intake
pre-check with product-copy banners, and attachment-error reasons mapped to
localized copy.

docs/config-catalog.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write docs/config-catalog.md
-config-catalog.md: e7ab120218c6de909bbd799c19b38eef524c7555
-config-catalog.zh.md: 622a0372de2f194e7063312ad7b8343a0bc58f06
+config-catalog.md: 40a10696f65b4e63c2cf14b4c3e3793c61b34e0d
+config-catalog.zh.md: 91242e41c61ae049c48caad6f30ba9d217e5d16c

docs/config-catalog.md

@@ -357,7 +357,7 @@ export interface ConnectionConfig {
 }
 ```
 
-Source: [`packages/client/connection/src/index.ts:52`](../packages/client/connection/src/index.ts)
+Source: [`packages/client/connection/src/index.ts:50`](../packages/client/connection/src/index.ts)
 
 ## `@deepseek-ai/dsh-client-hmr`
 

docs/config-catalog.zh.md

@@ -359,7 +359,7 @@ export interface ConnectionConfig {
 }
 ```
 
-来源：[`packages/client/connection/src/index.ts:52`](../packages/client/connection/src/index.ts)
+来源：[`packages/client/connection/src/index.ts:50`](../packages/client/connection/src/index.ts)
 
 ## `@deepseek-ai/dsh-client-hmr`