add session summary: Mar 1 upload pipeline + filesystem consolidation

Session_Summaries/2026-03-01_Upload-Pipeline-Filesystem-Consolidation.md

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+# Session Summary – March 1, 2026
+## Upload Pipeline + Filesystem Consolidation
+
+Direct runtime upload model implemented and confirmed. Filesystem architecture docs consolidated.
+
+---
+
+## What Shipped
+
+### Upload Model
+- Implemented direct runtime upload model
+- Removed staging and symlink exploration entirely
+- Uploads write atomically to runtime root
+- Enforced by strict allowlist (`mods/*.jar`, `world/datapacks/*.zip`)
+
+### Provenance
+- Added `.zlh_metadata.json` provenance tracking
+- Extended `stat` response with `source` field (`"user" | null`)
+- No curated inference implemented (intentional)
+
+### API Transport
+- Identified `fetch()` streaming as source of upload proxy timing issues
+- Switched to raw `http.request` piping (`req.pipe(proxyReq)` / `proxyRes.pipe(res)`)
+- Confirmed agent upload via direct curl
+- Upload timeout tuning identified as remaining work
+
+### Documentation
+- Consolidated filesystem architecture docs (`filesystem-and-file-browser.md`, `mod-deployment-safety.md`)
+- Full zlh-grind repo consolidation pass (README, CONSTRAINTS, OPEN_THREADS, SESSION_START, ANTI_DRIFT, UPSTREAMS)
+
+---
+
+## System State
+
+- Read: Stable
+- Write: Stable with shadow backup
+- Delete: Constrained and safe
+- Upload: Implemented, transport tuning in progress
+- Console: Stable
+
+---
+
+## Remaining Focus
+
+- Upload transport diagnostics (distinguish client abort / upstream timeout / socket reset)
+- Increase upload route timeout
+- Dev server filesystem model planning (not yet designed)