refactor(cli): rename plan lifecycle-list and lifecycle-apply to match specification

Renames `plan lifecycle-list` to `plan list` and `plan lifecycle-apply` to `plan apply` to align with the specification's canonical command names. Removes legacy V2 plan commands that occupied those names.

- Renamed CLI command registrations from lifecycle-list/lifecycle-apply to list/apply
- Removed legacy V2 apply and list commands (~200 lines)
- Updated apply shortcut in main.py to delegate to v3 lifecycle
- Added defensive null check for plan existence in apply command
- Updated 63+ test, doc, and benchmark files for consistency

Closes #881

Co-authored-by: Jeffrey Phillips Freeman <the@jeffreyfreeman.me>
Co-committed-by: Jeffrey Phillips Freeman <the@jeffreyfreeman.me>

robot/helper_cli_lifecycle.py

@@ -248,7 +248,7 @@ def plan_apply_changeset() -> None:
     with patch(
         "cleveragents.cli.commands.plan._get_lifecycle_service", return_value=svc
     ):
-        result = runner.invoke(plan_app, ["lifecycle-apply", "--yes", _PLAN_ULID])
+        result = runner.invoke(plan_app, ["apply", "--yes", _PLAN_ULID])
         if result.exit_code != 0:
             _fail(f"plan apply rc={result.exit_code}\n{result.output}")
 
@@ -309,7 +309,7 @@ def full_lifecycle() -> None:
             assert r2.exit_code == 0, f"plan use: {r2.output}"
             r3 = runner.invoke(plan_app, ["execute", _PLAN_ULID])
             assert r3.exit_code == 0, f"plan execute: {r3.output}"
-            r4 = runner.invoke(plan_app, ["lifecycle-apply", "--yes", _PLAN_ULID])
+            r4 = runner.invoke(plan_app, ["apply", "--yes", _PLAN_ULID])
             assert r4.exit_code == 0, f"plan apply: {r4.output}"
 
         cs = store.get(cid)