feat(studio): central error helpers + inline log viewer + Today CTAs

Bundles the error-UX overhaul and the inline log viewer:

  - New `FaiLog` (`~/.fai/logs/studio-errors.log`, 256 KiB rotation,
    JSON-per-line). Every operator-visible failure is appended so
    `fai admin doctor` and the new viewer can show the trail
    without the operator having to reproduce the failure.
  - New `showFaiErrorSnack` / `showFaiErrorDialog` helpers wrap
    `FaiErrorBox` in copyable surfaces; 27 ad-hoc
    `SnackBar(content: Text(e.toString()))` sites swept to use
    them (settings, doctor, audit, store, module sheet, system-AI
    editor, flow output).
  - New `FaiLogViewer` modal (`showFaiLogViewer`) renders log
    files inline with line numbers, JSON-key + `[level]` token
    colouring, Copy-all, Refresh, Open-externally. Doctor's
    daemon-paths panel grows a "View" button next to "Open" for
    every `.log` row and now also lists the Studio errors log.
  - Today carousel: CTAs now actually re-run search after a
    `filterCategory` / `runQuery` story is tapped (was only
    flipping the chip state). Fallback story list bumped to 8.
  - Editor bumped to git ref carrying 0.15.0 (type-token
    colouring + analyzer diagnostics).

Studio bumped to 0.62.0.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/widgets/fai_system_ai_editor.dart

@@ -6,6 +6,7 @@
 
 import 'package:flutter/material.dart';
 
+import '../data/error_presentation.dart';
 import '../data/hub.dart';
 import '../l10n/app_localizations.dart';
 import '../theme/theme.dart';
@@ -249,10 +250,7 @@ class _FaiSystemAiEditorState extends State<FaiSystemAiEditor> {
       });
     } catch (e) {
       if (!mounted) return;
-      final l = AppLocalizations.of(context)!;
-      ScaffoldMessenger.of(context).showSnackBar(
-        SnackBar(content: Text(l.systemAiCacheClearFailed(e.toString()))),
-      );
+      showFaiErrorSnack(context, 'settings.system-ai.cache-clear', e);
     }
   }