fix(webui): pending reply notice until the seat answers, relative Age (#1507)

Dewey's return-flow candidate on the #1512 R1 baseline. The inspector used to
show the previous answer while a seat worked on a reply, which looked like the
reply; it now shows a pending notice that clears on the new final answer.
Age shows a relative time beside the ISO time. Filbert approved R2, source
only; the patch reproduces the pinned hashes (app.js d1a51646,
return-flow.test.mjs a598c0d4). webui tests 9/9, all eight suites green.
Known limits are in agents/dewey/work/return-flow-age/NOTES.md. Not pushed.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

BUILD-LOG.md

@@ -2872,3 +2872,30 @@ files lose HEAD lines only where a row was deliberately edited.
 Evidence: all eight suites green on the working tree (config 24, task 90,
 foundation 43, conductor 17, release 14, auth 15, discord 63,
 extension-package 18). Not pushed.
+
+## 2026-09-26: WebUI return flow and Age (#1507, Console change)
+
+Before: after a reply from the WebUI the inspector kept a pending notice even
+once the seat had answered, and the Age column read from the wrong field.
+After: the pending notice clears once the seat's next answer arrives and stays
+cleared, and Age follows the session's last activity. Dewey authored it on
+the #1512 R1 baseline (`app.js` ce7d79a4). Filbert asked for revisions in R1
+(wrong failing assertion named in NOTES, no test that the notice stays
+cleared) and approved R2, source only, after a mutation check that deletes the
+clearing loop fails the new test.
+
+Evidence: `candidate.patch` applied to HEAD reproduces the pins (`app.js`
+d1a51646, `tests/return-flow.test.mjs` a598c0d4); webui tests 9/9; eight
+suites green. Record: `agents/dewey/work/return-flow-age/`. Limits are listed
+in its NOTES.md: a send made while the seat is still working can be cleared by
+the previous answer, and the card and table still show the old preview. The
+fixture reproduces the misleading pending display, not Jason's live report of
+no return at all. Not pushed; the live WebUI reads the file from disk.
+
+Correction (Sage, same day): the Before and After lines above misdescribe the
+change. On the baseline the inspector showed no pending notice at all; while
+the seat worked on a reply it showed the previous answer as "Last assistant
+text", which looked like the reply. Age showed only the ISO time. The
+candidate adds a pending notice that appears after a send and clears once the
+new final answer arrives, and Age shows a relative time ("1m ago") beside the
+ISO time. Source: `agents/dewey/work/return-flow-age/NOTES.md`.