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/data/error_presentation.dart

@@ -0,0 +1,114 @@
+// Single entry point for surfacing an error to the operator.
+// Every error pathway Studio shows (SnackBar, dialog, inline
+// strip) should go through one of these helpers so the
+// operator gets:
+//
+//   • a copyable, selectable rendition of the message
+//   • a friendly headline (gRPC codes mapped via
+//     friendlyError) instead of a wall-of-stack-trace
+//   • an automatic append to ~/.fai/logs/studio-errors.log so
+//     the trail survives the dismiss action
+//
+// Call sites used to scatter `ScaffoldMessenger.of(ctx).showSnackBar(
+// SnackBar(content: Text(e.toString())))` — that violated the
+// "errors must be copyable" rule everywhere. These helpers
+// replace those open-coded sites.
+
+import 'package:flutter/material.dart';
+
+import '../widgets/fai_error_box.dart';
+import '../theme/tokens.dart';
+import 'fai_log.dart';
+
+/// Show [error] as a SnackBar with a copy affordance.
+///
+/// [source] is a short tag (`flows.run`, `audit.clear`, …)
+/// used to group entries in the on-disk log so an operator or
+/// `fai doctor` can scan recent failures by area without
+/// reading the full free-text. Keep it stable; treat it like
+/// a metric label, not free-form text.
+///
+/// [context] is the build-context the snack lands on. Falls
+/// back to a Material default duration of 6 seconds — twice
+/// the framework default so the operator has time to click
+/// copy on an unfamiliar message.
+void showFaiErrorSnack(
+  BuildContext context,
+  String source,
+  Object error, {
+  String? title,
+  Duration duration = const Duration(seconds: 6),
+}) {
+  // Fire-and-forget log write. If the disk's full or the dir
+  // is read-only the UI still surfaces the error.
+  FaiLog.instance.error(source, error, context: title);
+  final messenger = ScaffoldMessenger.maybeOf(context);
+  if (messenger == null) {
+    // No Scaffold above — the caller is likely showing the
+    // error from inside a dialog. We've already logged; bail
+    // rather than throw.
+    return;
+  }
+  messenger.hideCurrentSnackBar();
+  final theme = Theme.of(context);
+  messenger.showSnackBar(
+    SnackBar(
+      duration: duration,
+      behavior: SnackBarBehavior.floating,
+      // Default SnackBar padding crushes our error box; reset
+      // to zero and let the box's own padding take over.
+      padding: EdgeInsets.zero,
+      content: Padding(
+        padding: const EdgeInsets.symmetric(
+          horizontal: FaiSpace.sm,
+          vertical: FaiSpace.xs,
+        ),
+        child: Column(
+          mainAxisSize: MainAxisSize.min,
+          crossAxisAlignment: CrossAxisAlignment.stretch,
+          children: [
+            if (title != null) ...[
+              Text(
+                title,
+                style: theme.textTheme.titleSmall?.copyWith(
+                  color: theme.colorScheme.error,
+                  fontWeight: FontWeight.w600,
+                ),
+              ),
+              const SizedBox(height: FaiSpace.xs),
+            ],
+            FaiErrorBox(error: error, isError: true),
+          ],
+        ),
+      ),
+    ),
+  );
+}
+
+/// Show [error] as a centered modal dialog. Use this when the
+/// failure blocks meaningful interaction (auth missing, hub
+/// unreachable) — a SnackBar would be too easy to dismiss.
+Future<void> showFaiErrorDialog(
+  BuildContext context,
+  String source,
+  Object error, {
+  String? title,
+}) async {
+  FaiLog.instance.error(source, error);
+  return showDialog<void>(
+    context: context,
+    builder: (ctx) => AlertDialog(
+      title: title == null ? null : Text(title),
+      content: SizedBox(
+        width: 480,
+        child: FaiErrorBox(error: error, isError: true, maxHeight: 240),
+      ),
+      actions: [
+        TextButton(
+          onPressed: () => Navigator.of(ctx).maybePop(),
+          child: const Text('OK'),
+        ),
+      ],
+    ),
+  );
+}