Fix stale semantic web-search rows sticking at bottom after rollout commit #191

Problem

A saved debug bundle shows committed Codex rollout rows for web search already rendered in the transcript while the live proxy semantic history still renders the same web-search activity at the bottom of the feed.

Bundle:

/Users/juliusolsson/.config/agent-code/debug-bundles/2026-05-17T12-02-35-745-19d02c20

Evidence from the bundle:

• html-clean.html has committed rollout rows such as 2026-05-17T12:01:20.152Z:web_search_call, 2026-05-17T12:01:37.425Z:web_search_call, and 2026-05-17T12:01:51.946Z:web_search_call.
• The same HTML also has live semantic web-search rows at the bottom: 🌐 Search: Electron window.prompt... and 🌐 Search: site:electronjs.org....
• render-diagnostics.json shows archived proxy turns such as resp_06c0839... and resp_0365a73... still have renderUnitCount > 0 because finalized web_search_call blocks have no toolId/callId, so committed tool ownership cannot suppress them.
• Empty finalized reasoning blocks are also counted as render units even though SemanticLiveBlockRow renders null for empty reasoning.

Expected

Once Codex rollout has committed the web-search rows and final assistant text, archived proxy semantic history should not keep rendering duplicate web-search activity at the bottom.

Likely fix

Make the semantic render-unit ownership layer match actual visible rows:

• empty reasoning/thinking blocks should not emit render units
• finalized provider-native activity blocks without correlation ids, such as web_search_call, should yield when the same Codex turn has committed rollout ownership for those activity rows
• add regression coverage based on the 2026-05-17 bundle shape

This is a follow-up to the semantic-first rendering stack and the render ownership fixes in #186.