docs(architecture): file Q-109 — cascade generation-source dispatch

Surfaced during #957 zone-selection authoring: a body's setting/mode should
dispatch the cascade entry to planetary / station / mod-DLC-forked /
save-only(player_base) sources, distinct from setting's in-path tweaker role.
Captured as an open question so #957 stays scoped to the planetary path; this is
why #957's zone table excludes station-only zone ids.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

decisions/questions-architecture.md

@@ -419,4 +419,12 @@ Technical foundation questions: engine, protocols, data structures, performance,
 
 ---
 
-*57 questions (11 resolved, 1 partially resolved, 45 open). Last updated: 2026-05-31.*
+### Q-109: Cascade generation-source dispatch — planetary / station / mod-DLC-forked / save-only
+- **Status:** Open — raised by Jeroen (2026-06-05, during #957 zone-selection authoring)
+- **Question:** The generation cascade currently has a single implicit path: every body runs the planetary generator (`run_cascade` → Layers 0–5). But a body's `SettingType` (or a sibling `GenerationSource` discriminator) should **dispatch at the cascade entry** to one of several generation sources: (a) **planetary** — the default terrain→quarter→tile cascade (#955/#956/#957…); (b) **station / orbital** — a *separate* cascade that owns the station-only zone types (`residential_station`, `extraction_space`, `port_space`, `rural_orbital`) and its own layout model, rather than branching the planetary code (this is why #957's zone-selection table deliberately excludes those ids — see [D-229](architecture.md#d-229) amendment 2026-06-05); (c) **mod / DLC-forked** — a value that routes generation to externally-provided code/templates (a mod or DLC name), so third-party content can supply a body's built form without patching core; (d) **save-only / `player_base`** — disables auto-generation entirely and loads the body's built world from a save file (player-constructed bases must persist, not regenerate). Where does this discriminator live — on `SettingType` itself (it already carries `Station`/`Orbital` variants) or a dedicated `GenerationSource` enum at the `run_cascade` entry? How does the mod/DLC fork resolve to external code (registry? trait object? content-pack manifest?)? And how does save-only compose with the D-203 hot cache and the D-225 compute-on-demand proxy (a `player_base` body must never enqueue an `AnalyzeBody`)?
+- **Context:** Surfaced while authoring #957's `(ZoningType × economic_role × setting)` zone-selection table: `setting` is the right *tweaker* within the planetary path, but it is also the natural *dispatch* point above it — the two roles are distinct and only the tweaker belongs in #957. The dispatch is a cross-cutting routing seam above any single layer; capturing it here so #957 stays scoped to the planetary path. Not blocking — the planetary path is the only live source today. Wants Tyre (cascade architecture) + a look at modding/DLC strategy and the savegame model (Phase 5+) before it's decided.
+- **Cross-reference:** [D-200](architecture.md#d-200) (runtime cascade), [D-225](architecture.md#d-225) (compute-on-demand proxy — save-only must bypass), [D-203](architecture.md#d-203) (hot cache), [D-229](architecture.md#d-229) (zone-selection — excludes station ids for this reason), D-222 (Quarter/spatial tiers), and the development cascade (Phase 5 player control + savegame)
+
+---
+
+*58 questions (11 resolved, 1 partially resolved, 46 open). Last updated: 2026-06-05.*

decisions/questions.md

@@ -6,7 +6,7 @@ Tracked questions awaiting discussion or resolution. Split by domain, mirroring
 
 | File | Domain | Questions |
 |------|--------|-----------|
-| [questions-architecture.md](questions-architecture.md) | Technical foundation | Q-001, Q-006, Q-009, Q-018–Q-023, Q-029, Q-030, Q-046, Q-059, Q-060, Q-063–Q-094 |
+| [questions-architecture.md](questions-architecture.md) | Technical foundation | Q-001, Q-006, Q-009, Q-018–Q-023, Q-029, Q-030, Q-046, Q-059, Q-060, Q-063–Q-094, Q-096–Q-109 |
 | [questions-perception.md](questions-perception.md) | Player observation | Q-003, Q-014, Q-016, Q-024, Q-025, Q-026, Q-051, Q-053, Q-054 |
 | [questions-content.md](questions-content.md) | Narrative, NPCs, setting | Q-010, Q-012, Q-013, Q-015, Q-017, Q-028, Q-031, Q-033, Q-040–Q-045, Q-047–Q-050, Q-052, Q-056, Q-057, Q-095, Q-WTF-039, Q-WTF-040, Q-WTF-041 |
 | [questions-scope.md](questions-scope.md) | Game concept, prototype | Q-002, Q-004, Q-005, Q-007, Q-008, Q-011, Q-027, Q-032, Q-034–Q-039, Q-058, Q-061, Q-062 |