Phase 0: scaffold tree + manifest

- README, .gitignore, CLAUDE.md (project conventions)
- docs/PHASE0.md — full Phase 0 manifest (locked substrate)
- 10 root .lua modules + 4 ffi/ bindings, all stubs raising NotImplemented
  with module-scoped responsibilities matching the manifest
- config.lua wired to current dirac/hossenfelder endpoints (qwen-coder-7b
  snappy/32k + cloud via OpenRouter through hossenfelder)

File names match docs/PHASE0.md §4 exactly. Module bodies fill in across
later phases; the tree shape is locked.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ffi/libc.lua

@@ -0,0 +1,18 @@
+-- ffi/libc.lua — shared libc bindings: errno, signal, write, read, chdir.
+
+local ffi = require("ffi")
+
+ffi.cdef[[
+int   chdir(const char *path);
+int   errno;
+char *strerror(int errnum);
+]]
+
+local M = {}
+
+-- Apply chdir per PHASE0.md §7 (intercepts `cd` so wd persists across popen).
+function M.chdir(path)
+    error("libc.chdir: not implemented (Phase 0 pending)")
+end
+
+return M