feat(studio): typed flow outputs + on-disk docs + UX polish

Documentation system (the original "whole docs system is broken"
complaint):
- Studio reads inline docs from disk via the new
  getInstalledModuleDocs RPC. No network, no auth, no provider
  lock-in.
- store.dart probes for MODULE.md eagerly when a module-detail
  sheet opens (a single file stat). The Documentation section
  only renders when the bundle actually shipped docs.
- Shared FaiTheme.markdownStyle helper used by Welcome's
  DocReaderSheet and Store's DocsPanel so every inline doc
  reads in the same typography. The shared style forces
  code.backgroundColor = transparent to suppress the per-span
  bands flutter_markdown's default code style draws on dark
  themes.

Flow run dialog:
- Run-button gating now strips the @version suffix from
  installed capabilities before the contains() check. Without
  this fix the button stayed disabled for every flow with
  dependencies, even after a successful install.
- Studio derives a MIME type from the picked file's extension
  (small per-suffix map; .pdf, .docx, .txt, .json, ...) and
  forwards it to the hub. Fixes "unsupported MIME type:
  application/octet-stream" from text.extract.
- Dialog title tracks the future's state: running -> "extract
  laeuft", success -> "extract -- Ergebnis", failure ->
  "extract -- fehlgeschlagen".
- Output rendering moved from String stringification to a
  sealed FlowOutput type (Text / Json / Bytes / File / Unknown).
  A new FaiFlowOutput widget dispatches per variant: markdown
  for text/markdown (heuristic), pretty JSON for proto Struct,
  inline image preview + Save-As for bytes, Open for file URIs.

Byte sizes:
- New humanBytes() helper renders 23.3 kB / 1.04 MB style values
  with three significant digits, matching Finder / GNOME Files.
  Wired into flow-card pills, picked-file readouts, and the
  bytes-payload preview line.

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

lib/l10n/app_localizations.dart

@@ -2282,6 +2282,18 @@ abstract class AppLocalizations {
   /// **'Running {name}'**
   String flowsRunningTitle(String name);
 
+  /// No description provided for @flowsResultTitle.
+  ///
+  /// In en, this message translates to:
+  /// **'{name} — result'**
+  String flowsResultTitle(String name);
+
+  /// No description provided for @flowsErrorTitle.
+  ///
+  /// In en, this message translates to:
+  /// **'{name} — failed'**
+  String flowsErrorTitle(String name);
+
   /// No description provided for @flowsRunning.
   ///
   /// In en, this message translates to:
@@ -2294,6 +2306,54 @@ abstract class AppLocalizations {
   /// **'Flow completed with no declared outputs.'**
   String get flowsNoOutputs;
 
+  /// No description provided for @flowsOutputUnknown.
+  ///
+  /// In en, this message translates to:
+  /// **'Output payload variant not recognised.'**
+  String get flowsOutputUnknown;
+
+  /// No description provided for @flowsOutputBytesUnknownMime.
+  ///
+  /// In en, this message translates to:
+  /// **'binary'**
+  String get flowsOutputBytesUnknownMime;
+
+  /// No description provided for @flowsOutputSaveAs.
+  ///
+  /// In en, this message translates to:
+  /// **'Save as…'**
+  String get flowsOutputSaveAs;
+
+  /// No description provided for @flowsOutputSaveAsTitle.
+  ///
+  /// In en, this message translates to:
+  /// **'Save flow output'**
+  String get flowsOutputSaveAsTitle;
+
+  /// No description provided for @flowsOutputSavedAt.
+  ///
+  /// In en, this message translates to:
+  /// **'Saved to {path}'**
+  String flowsOutputSavedAt(String path);
+
+  /// No description provided for @flowsOutputSaveFailed.
+  ///
+  /// In en, this message translates to:
+  /// **'Save failed: {error}'**
+  String flowsOutputSaveFailed(String error);
+
+  /// No description provided for @flowsOutputOpen.
+  ///
+  /// In en, this message translates to:
+  /// **'Open'**
+  String get flowsOutputOpen;
+
+  /// No description provided for @flowsOutputOpenFailed.
+  ///
+  /// In en, this message translates to:
+  /// **'Open failed: {error}'**
+  String flowsOutputOpenFailed(String error);
+
   /// No description provided for @approvalsTitle.
   ///
   /// In en, this message translates to: