Participant episode/reset & budget/quota: semantics + language surfaces + model (SEM-222, SEM-223, DSL-120, DSL-121, ACT-623, ACT-624)

[Brad-Edwards]

Joint design issue — SEM-222/223, DSL-120/121, ACT-623/624
Anchor UID for branch-CI: SEM-222
Priority: MUST | Wave TBD | Status: DRAFT (all)

Why this is one issue

Six requirements across three layers form one coherent episode + budget model: SEM (semantics), DSL (surfaces), ACT (model). The three layers interlock.

Scope of this issue

Joint design (ADR + formal spec + language surfaces + model). PRs use branch UID SEM-222.

Spawned implementation issues

• Participant Episode, Reset, And Termination Semantics (SEM-222) #305 — SEM-222
• Participant Budget, Quota, And Exhaustion Semantics (SEM-223) #306 — SEM-223
• Participant Episode Structure And Termination Surface (DSL-120) #307 — DSL-120
• Participant Interaction Budget Surface (DSL-121) #308 — DSL-121
• Participant Episode Structure (ACT-623) #309 — ACT-623
• Participant Interaction Budgets And Quotas (ACT-624) #310 — ACT-624