fix(queen): lane credits follow the turn that wrote the branch, not only accepted ones

[dmitrii-f-t27]

Follow-up to #527.

• Measured live: /queen/public-credits credited 406 issues. Of the 514 queen-<issue> PRs merged into t27 since 2026-09-17, only 89 had an accepted turn.
• The maintainer merged the rest after a sendBack, escalate or wait verdict.
• The merge is what puts the work on master. So the credited lane is now the lane of the issue's latest turn, whose work the branch carries.
• Tests are updated, and the queen-lane-credits and route tests pass.

Dmitrii Fedorov (@dmitrii-f-t27)

[github-actions]

✅ Tests passed — 2500/2560

Suite	Passed	Failed	Skipped
✅ agent	87/87	0	0
✅ build	9/9	0	0
✅ cdp-protocol	5/5	0	0
✅ eval	93/93	0	0
✅ server-agent	280/280	0	0
✅ server-api	1349/1408	0	59
✅ server-browser	6/6	0	0
✅ server-integration	10/11	0	1
✅ server-lib	279/279	0	0
✅ server-pglive	25/25	0	0
✅ server-root	68/68	0	0
✅ server-skills	31/31	0	0
✅ server-tools	244/244	0	0
✅ shared	14/14	0	0

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