Merge latest origin/master into feat/tui-package

Bring in the one-session surface manager landed through #376 after master advanced beyond the prior merge base.

Resolve the generated event-matrix overlap by regenerating from the merged TypeScript tree, preserving master's updated session declaration locations together with the TUI listener edges. Regenerate and verify the RFC index so both lifecycle updates remain represented.

docs/rfc/INDEX.md

@@ -23,7 +23,6 @@ Generated by `pnpm run gen-rfc-index` from the RFC tree — never edit by hand;
 | [Prune dead public and result surface](proposed/simplification/2026-07-04-prune-dead-core-spine-surface.md) | 2026-07-04 |
 | [Make JSON-RPC completion and transport directional](proposed/simplification/2026-07-19-make-jsonrpc-directional.md) | 2026-07-19 |
 | [Retire the standalone subagent mock package](proposed/simplification/2026-07-19-retire-subagent-mock-package.md) | 2026-07-19 |
-| [Use one surface manager per session](proposed/simplification/2026-07-19-use-one-session-surface-manager.md) | 2026-07-19 |
 
 ### Architecture
 
@@ -118,6 +117,7 @@ Generated by `pnpm run gen-rfc-index` from the RFC tree — never edit by hand;
 | [Drop unconsumed skill provider events](implemented/simplification/2026-07-12-drop-unconsumed-skill-provider-events.md) | 2026-07-12 |
 | [Prune unused web seam fields](implemented/simplification/2026-07-12-prune-unused-web-seam-fields.md) | 2026-07-12 |
 | [Simplify session-log representation](implemented/simplification/2026-07-12-simplify-session-log-representation.md) | 2026-07-12 |
+| [Use one surface manager per session](implemented/simplification/2026-07-19-use-one-session-surface-manager.md) | 2026-07-19 |
 
 ### Architecture