fix(profiles): per-profile lifecycle config, real prefs purge (SPEC-50)

Four more review findings:

- profile_lifecycle / profile_runtime: lifecycle actions target arbitrary
  profiles, but the CLI path and endpoint args came from the ACTIVE profile's
  config. Starting profile B from A's window therefore used A's configured
  binary and, since `start` passed no `--port`, launched B's daemon on the CLI
  default (7777) — colliding with the legacy daemon or landing on an endpoint
  B's own ServerConfig disagreed with. ProfileLifecycle now takes `cliPathFor`
  and `serveArgsFor`, wired to the target's scoped ServerConfig, and
  MakitCliResolver.resolve() accepts a per-call override.
- profile_deleter: actually purge the profile's preference keys (store 3). The
  unconditional skip was based on the obsolete `SharedPreferences.setPrefix`
  assumption; prefs are now scoped by key prefix, so `ProfileScopedPrefs
  .clearScope()` can purge a non-active profile. Injected as `purgePrefs`, so
  contexts with no prefs still report the store honestly. The delete sheet lists
  prefs under "Will be deleted" again, and its caveat note is gone.
- profile_deleter: a regular file at `home` is no longer reported as removed
  while `deleteDirectory` silently no-ops on it — `ProfileFileSystem` gains
  `isDirectory`, and the file case is erased with `deleteFile` and named in the
  result.
- profiles_section: `promptCreateProfile` catches a throwing `create` (unwritable
  registry, failed port allocation) and reports it, instead of leaking an
  unhandled async error with no user feedback.

Author: leduckhc

app/lib/desktop/settings/sections/profile_delete_sheet.dart

@@ -9,8 +9,8 @@
 /// The confirm wires to [ProfileDeleter], then reflects its
 /// [ProfileDeletionResult] honestly: on refusal it surfaces the reason from
 /// `skipped`; on success it reports the bytes freed **and** the stores that were
-/// skipped (notably the `NSUserDefaults` keys the deleter cannot purge from this
-/// process — SPEC-50 D11), never hiding them.
+/// skipped (for example the secure-store file on a platform that has none),
+/// never hiding them.
 library;
 
 import 'package:flutter/material.dart';
@@ -128,6 +128,11 @@ class _ProfileDeleteDialog extends StatelessWidget {
                 'this profile’s TLS identity',
               ),
               const _DeletedItem('keychain / secure store', 'pairing bearer'),
+              // Genuinely deleted now: prefs are scoped by key prefix, so the
+              // deleter can purge another profile's keys (the sheet used to carry
+              // a caveat here, from when the global setPrefix made them
+              // unreachable).
+              _DeletedItem('prefs', 'flutter.$prefsKeyPrefix* keys'),
               const _DeletedItem('profiles.json', 'registry entry'),
               const SizedBox(height: kSpace16),
               _SectionLabel(label: 'Will be kept', color: cs.primary),
@@ -139,18 +144,6 @@ class _ProfileDeleteDialog extends StatelessWidget {
                 'other profiles',
                 'every other profile is unaffected',
               ),
-              const SizedBox(height: kSpace12),
-              // Honest caveat: prefs cannot be purged from this process while
-              // another profile's prefix is pinned (SPEC-50 D11), so the sheet
-              // must not list them under "Will be deleted" — the deletion reports
-              // them as skipped.
-              Text(
-                'A few app preferences (flutter.$prefsKeyPrefix*) are left '
-                'behind for now — they can’t be purged from another profile.',
-                style: Theme.of(
-                  context,
-                ).textTheme.bodySmall?.copyWith(color: cs.outline),
-              ),
               if (running) ...[
                 const SizedBox(height: kSpace12),
                 Text(

app/test/desktop/settings/profiles_section_test.dart

@@ -460,8 +460,9 @@ void main() {
     );
     expect(successes, isNotEmpty);
     expect(successes.last.title, contains('Deleted feat-profiles'));
-    // The NSUserDefaults keys the deleter cannot purge are surfaced, not hidden.
-    expect(successes.last.detail, contains('NSUserDefaults'));
+    // Stores the deleter could not purge are surfaced, not hidden. This wiring
+    // has no prefs, so the prefs store is honestly reported as skipped.
+    expect(successes.last.detail, contains('preference keys'));
     // The registry entry is gone, so the row disappears.
     expect(find.text('feat-profiles'), findsNothing);
   });