Capture completion hints in command metadata

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Shell completion implementation plan
 
-Status: Stage 1 complete. Stage 2 is next.
+Status: Stages 1–2 complete. Stage 3 is next.
 
 Implement the [shell completion roadmap](completion.md) from baseline
 `2301872`. Follow the stages in order in one sprint. Intermediate stages may
@@ -62,6 +62,8 @@ this run; the focused adapter suite and the full interactive matrix pass.
 
 ## Stage 2: Capture completion hints
 
+Status: complete.
+
 1. Add the following public API in the root package. Add
    `Completion CompletionHint` to both `FlagMeta` and `ArgumentMeta`;
    existing binding constructors and their signatures stay in place.
@@ -97,6 +99,14 @@ this run; the focused adapter suite and the full interactive matrix pass.
    suggestions, repeated/captured bindings keep hints, and values absent from
    a suggestion list still reach the existing converter.
 
+Completion: added the public choice and hint constructors, carried hints through
+flag and operand bindings into neutral metadata, and supplied explicit boolean
+choices for built-in help and reporting flags. Focused tests cover copied
+choices, repeated and captured bindings, the empty-choice strategy, independent
+bridge copies, and execution of values outside the suggested choices. Root,
+internal adapter, and neutral metadata package tests pass with `GOWORK=off` and
+`GOTOOLCHAIN=local`.
+
 ## Stage 3: Install completion as an ordinary declaration
 
 1. Add `func Completion(executable string) Command`. The parameter is the