Preserve nested anchor activation and external-link disposition #531

Parent: #268. Webview epic: #264. Release epic: #227.

Proven gap

Unchanged Code OSS intercepts trusted primary anchor clicks, keeps same-document fragments local, posts other links to the host, and prevents middle auxclick. Native WebScene currently queues every uncancelled primary HTTP(S) anchor through one external request, does not preserve target/modifier/middle disposition, ignores auxiliary cancellation/default behavior, and can walk from a child document into its retained iframe owner.

Focused implementation

• Bound anchor lookup and fragment scrolling at the target document root.
• Keep unmodified same-document fragments local, including decoded IDs, #, and #top.
• Preserve _blank/named-target, Ctrl/Meta/Shift primary, and middle-click disposition on the existing typed external-URL request.
• Populate the activated anchor node ID without widening request authority.
• Honor auxclick.preventDefault() and never navigate for the right auxiliary button.
• Preserve the existing HTTP(S)-only and 8 KiB URL limits; download anchors remain separately owned.
• Add unchanged Code-shaped native and browser contracts.

Acceptance and deferred gates

• Implementation based on WebScene main 488b9790e1b14c83f06cdcbfdd220cd53f318d79.
• Focused regression sources authored.
• git diff --check passed.
• Execute Chromium/native contracts and exact unchanged webview acceptance.
• Run lifecycle, performance, memory, accessibility, and package gates.

Execution is deferred under the current implementation-first direction.