fix(#1437): add phase.list-plans to gsd-tools (#1485)

* fix(#1437): add phase.list-plans to gsd-tools

Register phase.list-plans in PHASE_COMMAND_ALIASES, implement
cmdPhaseListPlans in src/phase.cts (uses findPhaseInternal + scanPhasePlans
to return plan_count/has_plans/plans/phase_dir), and wire the handler in
phase-command-router. Previously every call produced "Unknown phase
subcommand".

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(#1437): register new test file in lint-test-file-count allowlist

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(#1437): rename test to fix-NNN convention; update file-count allowlist

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

src/command-aliases.cts

@@ -458,6 +458,14 @@ export const PHASE_COMMAND_ALIASES: CommandAlias[] = [
     ],
     "subcommand": "scaffold",
     "mutation": true
+  },
+  {
+    "canonical": "phase.list-plans",
+    "aliases": [
+      "phase list-plans"
+    ],
+    "subcommand": "list-plans",
+    "mutation": false
   }
 ];