* fix(updates): scope installed-version fallback to webui + verified current_sha (#5864 gate fixes)
Gate (Codex) found 2 CORE in the #5862/#5864 experimental-version-display fix:
1. api/updates.py:947 — the installed-version fallback ran in shared _check_repo_release
for BOTH repos, injecting WEBUI_VERSION (v0.52.0, not an Agent ref) into Agent payloads.
Now scoped to name=='webui'.
2. api/updates.py:996 — current_sha reused current_version_display, but WEBUI_VERSION can be
vX.Y.Z-dirty-<hash>/-N-g<sha>/bare-SHA/unknown (not git refs) -> broken /compare link +
lost update-summary subjects. current_sha now derives from a git-VERIFIED exact-match tag
(channel-neutral) or None; current_version keeps the real display string.
+2 regression tests (agent-repo-no-inject, dirty-HEAD-verified-sha). 21/21 update-channel green.
* changelog: #5864 experimental-channel version display fix (#5862)
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Co-authored-by: t <a@b>
