Keep nested help commands with application handlers

docs/roadmap/remediation.md

@@ -1,6 +1,6 @@
 # Performance implementation review findings
 
-Status: R-01 requires remediation.
+Status: R-01 complete; all recorded remediation work is addressed.
 
 Date: 2026-10-09.
 
@@ -36,8 +36,8 @@ The selected structure is present:
   configuration framing scans only the YAML preamble while retaining the
   selected full native and framed buffers.
 
-These changes implement PF-01–PF-06. The dispatch defect below is an ownership
-regression in the session integration, rather than a missing subsystem. The
+These changes implement PF-01–PF-06. The review identified an ownership
+regression in the session integration, corrected under R-01 below. The
 [internal overview](../internal/overview.md) owns the maintained package inventory.
 
 ## R-01: restrict built-in help interception to the root command
@@ -78,14 +78,14 @@ accepts it. No such additional restriction was selected.
 
 Required work:
 
-- [ ] Identify the root built-in help command by its complete selected path
+- [x] Identify the root built-in help command by its complete selected path
   or an equivalent explicit reserved-command identity. A root-path check such
   as `len(parsed.Path) == 1 && parsed.Path[0] == "help"` is sufficient for the
   current registry. Other runnable declarations must continue to their handler.
-- [ ] Add a public behavior regression for an application-owned nested `help`
+- [x] Add a public behavior regression for an application-owned nested `help`
   command. Verify it receives its typed input and that its handler outcome is
   preserved. Keep local `--help` and `help session help` as metadata operations.
-- [ ] Retain existing root help, invalid-target, usage, fresh-invocation,
+- [x] Retain existing root help, invalid-target, usage, fresh-invocation,
   registration-refresh, and diagnostic behavior. Use existing coverage where
   sufficient; verify the relevant regression and default suite after the fix.
 
@@ -93,7 +93,33 @@ Do not remediate this by rejecting nested `help` names or imposing new command
 naming rules. Keep the session optimization and established ownership boundary.
 Mark this item complete only after the correction and its evidence are recorded.
 
-## Evidence and limits
+### Completion evidence
+
+**Completed:** `App.Execute` now recognizes the built-in help command only when
+its selected path is the root `help` command. Nested application commands keep
+their existing handler path and naming freedom; session reuse is retained.
+
+The public regression `TestExecuteRunsApplicationOwnedNestedHelp` verifies a
+required typed operand reaches the nested handler and preserves its domain,
+status, and cause. Local `session help --help` and explicit `help session help`
+render the command's metadata without invoking that handler or requiring its
+execution operand.
+
+The regression first failed against the original dispatcher with the reported
+unexpected-input-type failure and passed after the correction. Focused validation
+and the full default suite passed with readonly, offline module access:
+
+```sh
+GOWORK=off GOTOOLCHAIN=local GOPROXY=off GONOPROXY=none GOSUMDB=off go test -mod=readonly -count=1 . -run '^TestExecuteRunsApplicationOwnedNestedHelp$'
+GOWORK=off GOTOOLCHAIN=local GOPROXY=off GONOPROXY=none GOSUMDB=off go test -mod=readonly -count=1 ./...
+```
+
+Existing root help, invalid-target, usage, fresh-invocation, registration-refresh,
+and diagnostic tests passed. Changed Go files were formatted; document links
+and whitespace checks passed. No new public contract or command-name restriction
+was introduced.
+
+## Original review evidence and limits
 
 - Reviewed the production diffs, changed behavioral tests, benchmark fixtures,
   architecture documentation, and completion/measurement records. Traced cache