Feat: Web loader

Loader/README.md

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+# Loader
+
+Tiny first-request bootstrap document for Moku.
+
+## Purpose
+
+The loader is intended to be the smallest possible first paint shown before the
+real application is handed off.
+
+Long term responsibilities:
+
+- capture original route intent
+- collect lightweight client capability hints
+- make a tiny boot decision
+- hand off to login or app
+
+## Route intent contract
+
+The loader writes bootstrap state to `sessionStorage`:
+
+- `moku.loader.intent` — the intended route path
+- `moku.loader.meta` — JSON metadata for the current bootstrap event
+
+The loader also writes a short-lived cookie:
+
+- `moku_loader_seen=1`
+
+The proxy uses that cookie to decide whether to keep serving the loader or to
+serve the real app document on the next request.
+
+## Current handoff behavior
+
+For now, the loader simply hands off to the originally requested route. That
+keeps the first implementation tiny while leaving a clear place to add auth or
+perf-tier decisions later.