Validate shell completion across supported shells

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Shell completion implementation plan
 
-Status: Stages 1–7 complete. Stage 8 is next.
+Status: Stages 1–8 complete.
 
 Implement the [shell completion roadmap](completion.md) from baseline
 `2301872`. Follow the stages in order in one sprint. Intermediate stages may
@@ -305,6 +305,8 @@ checks pass.
 
 ## Stage 8: Validate the assembled sprint
 
+Status: complete.
+
 1. Exercise the generated scripts in Bash, Zsh, and Fish using a built fixture
    executable, a disposable directory with filenames and directories containing
    spaces, and isolated shell configuration. Verify actual completion output
@@ -323,3 +325,21 @@ checks pass.
    dependency, and no changes to ordinary routing, flag acceptance, or report
    behavior outside the selected completion scope. Review documentation links,
    formatting, and the final diff. Record the actual validation results.
+
+Completion: the opt-in `TestCompletionConsumerInShells` builds a CommandKit
+fixture, generates its scripts, and verifies edited invocations and displayed
+descriptions in interactive Bash 5.3.9, Zsh 5.9, and Fish 4.2.1. The fixture
+uses isolated shell configuration and paths containing spaces. Run it with
+Python pexpect, Bash completion, and the three shells available using
+`COMMANDKIT_COMPLETION_SHELLS=1 GOTOOLCHAIN=local go test -count=1 -run
+'^TestCompletionConsumerInShells$' .`. Zsh and Fish were extracted to a
+disposable directory for this run; their executable, library, Zsh module, and
+function paths were supplied through `PATH`, `LD_LIBRARY_PATH`,
+`COMPLETION_ZSH_MODULE_PATH`, and `COMPLETION_ZSH_FUNCTION_ROOT`, respectively.
+The adapter's interactive
+transport matrix and additional short-equals and Unicode-basename checks also
+pass in all three shells. The root and both optional module suites pass in the
+local workspace, as does the root suite with `GOWORK=off`. Public GoDoc and
+dependency checks show no exposed backend types or reverse optional-module
+dependency. Existing execution suites, changed documentation links, formatting,
+and diff whitespace checks pass. The local workspace file is ignored.