add session summary: Feb 23 mod system operational

Session_Summaries/2026-02-23_Mod-System-Operational.md

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+# Session Summary – February 23, 2026
+## Mod System Now Operational
+
+Full mod lifecycle implemented and confirmed end-to-end.
+
+---
+
+## What Shipped
+
+### API
+- Modrinth search integrated (`GET /api/game/mods/search`)
+- Full install/list/enable/disable/delete routes live behind auth + ownership
+- Agent host allowlist expanded to include `cdn.modrinth.com`
+- Filename validation updated to allow `+` (required for Modrinth filenames like `sodium-neoforge-0.6.13+mc1.21.4.jar`)
+- Engine metadata bug fixed: `engineType="neoforge"`, `engineVersion="1.21.4"` (was `"minecraft"` / `"neoforge-1.21.4"`)
+- API → Agent payload contract corrected (field names and `source` field)
+
+### Frontend
+- Mod search drawer implemented
+- Installed mods panel implemented
+- Enable/disable/delete wired
+- Toast notifications added
+
+---
+
+## System State
+
+- Full lifecycle via API: ✅
+- Frontend search + install: ✅
+- Enable/disable/delete: ✅
+- Installed flag displayed: ✅
+- Soft delete to `/mods-removed`: ✅
+- No retention automation: intentional
+- No install queue: intentional
+- Filesystem authoritative: confirmed
+
+---
+
+## Known Tradeoffs Locked In
+
+- No deterministic Modrinth project ID persistence (installed detection is heuristic)
+- No DB tracking of mod state
+- Soft delete is permanent until file browser enables manual restore
+
+---
+
+## Pending at Session End
+
+- Response corruption investigation (one early curl output appeared malformed)
+- API error mapping: `"mod already exists"` → `409` (currently `502`)
+- Portal UI wiring for install flow