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/readline.lua

@@ -0,0 +1,15 @@
+-- ffi/readline.lua — GNU readline binding.
+-- Phase 0: readline + add_history + free. Phase 1: custom key bindings.
+-- See docs/PHASE0.md §9.
+
+local ffi = require("ffi")
+
+ffi.cdef[[
+char *readline(const char *prompt);
+void  add_history(const char *line);
+void  free(void *ptr);
+]]
+
+local M = {}
+-- Phase 0 stubs; wired with the REPL implementation.
+return M