📝 Improve docs after split

development/library.md

@@ -3,104 +3,4 @@
 The type-level design of the public API and the limitations it carries. The
 user-facing reference is [README § API](../README.md#api).
 
-## A type guard is the single primitive
-
-#### Decision (2026-09)
-
-Every pattern constructor returns a `Matcher<T>` whose only member is
-`matches: (value: unknown) => value is T`; `Pattern<T>` is an alias.
-
-#### Why
-
-- A type guard is the one TypeScript construct that both narrows in an `if` and
-  composes into a chain, so the library needs no DSL and no transpiler.
-- Because `matches` narrows, `match(value).with(pattern, handler)` types the
-  handler with no cast and no runtime tag.
-- `Pattern<T>` is an alias, so either name is the same type.
-
-## The builder is immutable
-
-#### Decision (2026-09)
-
-`.with` returns a new builder rather than mutating the current one.
-
-#### Why
-
-- A partially built chain can be stored and reused without one call site
-  affecting another.
-- `.with` widens the result type to `R | V`, which cannot be represented by a
-  value that changes type in place.
-
-## `exhaustive()` is a runtime check
-
-#### Decision (2026-09)
-
-`.exhaustive()` throws when no case matched; it does not statically prove that
-every member of the input union has a case.
-
-#### Why
-
-- Proving coverage through a fluent chain would need a compiler plugin or a
-  builder that tracks an uncovered-member set — out of proportion to this
-  library's size.
-- The union of handler return types is still type-safe; only the chain's
-  completeness is unchecked.
-
-#### Known issue
-
-- A missing case is a runtime `Error`, not a compile error. A caller wants
-  either an `.otherwise(...)` (which never throws) or to prove coverage
-  themselves. Tracking uncovered members is a possible future change.
-
-## `P.type` takes the type as a parameter
-
-#### Decision (2026-09)
-
-`P.type<T>(name)` requires the caller to supply `T`; it is not inferred from the
-`typeof` string.
-
-#### Why
-
-- A runtime string cannot carry a TypeScript type; the caller pairs the two, and
-  the compiler only checks that `T` is used consistently afterwards.
-
-#### Known issue
-
-- `T` and the runtime `name` can disagree (`P.type<number>("string")` compiles),
-  because nothing ties them together. Prefer `P.when` with a real type guard. A
-  name-to-type conditional mapping is a possible future change.
-
-## `P.shape` narrows only through `refine`
-
-#### Decision (2026-09)
-
-`P.shape<S, T>(shape, refine?)` returns `Matcher<T>`, defaulting to `Matcher<S>`
-without a `refine`.
-
-#### Why
-
-- The shape's values may be matchers, so `S` describes the check, not the value;
-  the `refine` guard is the explicit point where the value narrows to `T`.
-- Keys are checked with `in` rather than requiring an exact match, so a shape can
-  match a wider object — which is how discriminated unions are handled.
-
-#### Known issue
-
-- Without `refine` a discriminated-union case does not narrow, so `P.shape`
-  alone is easy to misuse. Prefer `P.when` when a guard is already available.
-
-## `P.any` exists for non-guard predicates
-
-#### Decision (2026-09)
-
-`P.any<T>(predicate)` takes a boolean predicate and a declared `T`.
-
-#### Why
-
-- Some checks are cheap as a boolean but awkward as a type guard (for example an
-  `every` over an array); `P.any` is the escape hatch.
-
-#### Known issue
-
-- As with `P.type`, the declared `T` is not proven by the predicate. Prefer
-  `P.when` whenever the check can be written as a guard.
+Currently the library is placeholder code.