feat(cli): 0.R4 - ludic deps sees through fn values (widest_reach) and lists the widest functions (--widest N, --reach N)

A step list or a registry of fn values takes no state and still reaches every state its steps take.
The compiler now writes `reach <n> <function>` - every state a function can come to by a call, a
`fn f` it writes or a global holding fn values it reads, to a fixed point - and ludic deps reports
widest_reach beside widest_function, with how many of those states the function does not take
(Maroon Lake: app_boot, 72, all 72 through fn values). --widest N lists the N functions that take the
most states with what each reaches; --reach N orders them by reach. A baseline without widest_reach
does not hold it until rewritten.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

LANGUAGE.md

@@ -381,7 +381,12 @@ program Pack {
 
 `ludic deps` reports the widest function - the most states any function or entry point of the
 program's own takes - and `--check` holds it as a ratchet like its other numbers
-(`widest_function 12` in the baseline file).
+(`widest_function 12` in the baseline file). A function value's states are supplied where it is called, so a
+step list - `let STEPS = [fn a, fn b]` walked by a function that takes nothing - hides what it
+touches; `widest_reach` is the most states any function can come to, through its calls, the `fn f`
+it writes and the globals holding fn values it reads (a registry of systems), and the report says how
+many of them it does not take itself. `ludic deps --widest N` lists the N functions that take the
+most states, each with what it reaches; `--reach N` lists them by reach.
 
 ### Types are checked before anything is emitted