Implement Organon, Ergasterion, Agon as routes in the web viewer

[mijahauan]

Context

The conceptual three-mode architecture from the original design — Organon (corpus browser), Ergasterion (transformation workshop), Agon (Endoporeutic Game arena) — remains the right framing. The Qt implementation that mirrored this as three windows was archived to archive/qt-gui-2025/ in May 2026 in favor of a web viewer (src/web_api/ FastAPI + src/web_viewer/ static SVG client) backed by the ELK layout engine.

The web viewer currently has the foundation laid (a viewer that loads an EGI and renders it via ELK + SVG) but does not yet surface the three modes. Implementing them is the next major UI workstream.

Suggested scope (split into sub-issues as needed)

Organon route (read-only browser)

• Tomos corpus listing + filter (by source: Peirce / Roberts / Sowa / Dau, by tags).
• Single-graph view: SVG render + EGIF / CGIF / CLIF / FOPL linear-form panels.
• Timeline / history view for graphs with UoD history.

Ergasterion route (interactive editor)

• Step-through proof construction using the existing headless RuleInteraction protocol (src/rule_interaction.py).
• Rule palette (ERA, INS, IT+, IT−, DC+, DC−) with polarity-aware enabling.
• Visual selection of subgraphs, target areas, and EGIF text input for INS.
• Branch / explore from any historical state (the DAG branching already exists in egi_transformation_history.py).

Agon route (Endoporeutic Game)

• Game setup UI: pick a domain model M and a proposal G; engine builds ~[ M ~[ G ] ].
• Move submission UI with role-switching (Graphist / Skeptic) and polarity enforcement.
• Outcome reporting using the existing EndoporeuticGame engine and the GameOutcome taxonomy (see docs/ENDOPOREUTIC_GAME_GUIDE.md).

Acceptance criteria for the umbrella issue

• Routing structure under src/web_api/routes/ with organon.py, ergasterion.py, agon.py.
• Static client UI under src/web_viewer/ with three top-level navigation entries.
• At least one end-to-end test per mode (browser → API → core).
• Updated README.md and docs/PRODUCT_VISION.md describing the mapping.