docs: record Askr North Star

AGENTS.md

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+# AGENTS.md
+
+Operational guide for `@askrjs/node`, the Node HTTP transport adapter for
+`@askrjs/server`.
+
+## Askr North Star
+
+Keep the transport flow narratable: a Node request becomes a Web `Request`, the
+server app returns a Web `Response`, and the adapter writes or cancels it.
+Enforce malformed configuration and impossible transport state at this boundary
+with actionable errors. Test disconnect, abort, streaming, timeout, and cleanup
+failure modes using real Node HTTP mechanisms. Do not fuse application routing
+or middleware policy into the adapter. Prefer explicit server and timeout
+configuration over environmental inference, and add adapter surface only for a
+demonstrated transport need.
+
+Run `npm run check` and the relevant HTTP benchmark before declaring a
+performance-sensitive change ready.
+
+## Optimization Gate
+
+A benchmark number is only half of an optimization's success criterion. The
+change must also preserve a causal path that a human or agent can narrate in one
+sentence.
+
+Every benchmark-driven change must include:
+
+1. the one-sentence causal description of the optimized path;
+2. the exact fallback trigger and proof that optimized and fallback paths have
+   identical observable behavior and error surfaces;
+3. an explicit legibility-cost statement, including `none` when no new path or
+   concept is introduced; and
+4. evidence that a measured bottleneck in a real application justifies the
+   optimization now.
+
+Prefer making the existing single path faster. New caches, inference,
+memoization, shortcuts, fast paths, or scheduler states require an explicit
+legibility decision; a speedup alone does not justify them.