WIP Add *local-names*

And use earmuff naming for `ContextVar`s

TODO: Implement LOCAL_NAMES context in lambda compilation.
TODO: Test.

src/hissp/__init__.py

@@ -36,6 +36,8 @@
 
 * from :mod:`hissp.compiler`:
 
+  * `*env*`
+  * `*local-names*`
   * `Compiler`
   * `evaluate`
   * `execute`
@@ -67,6 +69,8 @@
 `macros` available with the shorter ``hissp.._macro_`` `qualifier`.
 """
 from hissp.compiler import (
+    ENV as QzSTAR_envQzSTAR_,  # Munged form of *env*.
+    LOCAL_NAMES as QzSTAR_localQzH_namesQzSTAR_,  # Munged form of *local-names*.
     Compiler,
     evaluate,
     execute,

src/hissp/compiler.py

@@ -33,9 +33,9 @@
 _PARAM_INDENT = f"\n{len('(lambda ')*' '}"
 
 Env: TypeAlias = dict[str, Any]
-ENV: ContextVar[Env] = ContextVar("ENV")
+ENV: ContextVar[Env] = ContextVar("*env*")
 """
-Expansion environment.
+Expansion global environment.
 
 Sometimes a macro needs the current environment when expanding,
 instead of its defining environment.
@@ -44,6 +44,14 @@
 `readerless` and `macroexpand` use this automatically.
 """
 
+LOCAL_NAMES: ContextVar[frozenset[str]] = ContextVar("*local-names*")
+"""
+Local variable names in expansion scope.
+
+This does not include values (which don't exist yet) or globals.
+(See `ENV` for that).
+"""
+
 MAX_PROTOCOL = pickle.HIGHEST_PROTOCOL
 """
 Compiler pickle protocol limit.