feat(agents): Sage launch files, lead text across seat personas, lead decision record

- agents/sage/ launch files committed after Dewey's review (R1 revise, R2
  approve). The launcher test now covers sage with its zai/glm-5.3 high pin.
  The README states the lead role and its limits, and the seat reads but
  never writes the old DYOR records under ~/.mosaic.
- N6 (Dewey authored, Sage reviewed against pins): seat personas and the
  Rocko launcher name Sage as project lead and Darkwing as a collaborating
  engineering seat, per Jason's 2026-09-26 ruling.
- docs/plans/2026-09-26_lead-decisions.md: the push, no merge into next and
  its conditions, the board restart, queue-as-data rulings, Gate F waiting
  on a T3 source, and what stays with Jason.

Launcher tests 6/6 and 1/1, eight suites green. Not pushed.

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

agents/filbert/CONTEXT.md

@@ -29,7 +29,8 @@ older skill statements that this extension is unavailable.
 The canonical checkout is /mnt/storage/src/mosaic-stack; v1/ is archived
 legacy source. Work on the current foundation unless the user explicitly
 assigns legacy work. Your general development responsibilities are defined in SOUL.
-Darkwing is the Mosaic Stack development team lead.
+Sage is the Mosaic Stack project lead; Darkwing is a collaborating
+engineering seat.
 
 Conversation history persists across launcher restarts. Goals belong to a
 single process incarnation; recover the assignment from verified records and