Fix Markdown/bulk export review follow-ups from PR #19 (#20)

Apply the ten code-review findings on the freshly-merged Markdown +
bulk export workflow. No new features; correctness and UI/UX only.

Converter (tsv_odf_converter.py):

- _MD_LINE_START_RE: require whitespace (or end of string) after the
  digits-dot pattern so paragraphs starting with a decimal like
  "1.5 million" or "2025.06 release" are no longer mangled to
  "\1.5 million".
- _emit_kv: emit blank lines before and after so adjacent KV elements
  no longer collapse into one CommonMark paragraph and the bolded key
  stays visually distinct.
- _emit_paragraph: when DocElement.raw_lines preserved per-line breaks
  (multi-line addresses, poetry), emit each line with a CommonMark
  hard break (two trailing spaces) instead of collapsing into a single
  run-on line.

Markdown export UI (conclusion_export_mixin.py):

- _export_markdown_file: write to "<path>.tmp" then os.replace so a
  failed/cancelled conversion no longer destroys a pre-existing file
  the user picked to overwrite via FileDialog.
- _on_md_save_response: guard against Gio.File.get_path() == None
  (remote/MTP/GVfs locations) and surface a clear toast instead of an
  AttributeError swallowed as a generic "Export failed".
- _on_md_export_clicked → _on_md_save_response → _export_markdown_file
  → _on_md_export_finished: pass include_front_matter and open_after
  through the closure chain instead of self attributes, so overlapping
  per-row exports can no longer clobber each other's settings.
- _on_folder_chosen (bulk): show _EXPORT_FAILED_MSG on non-Dismiss
  errors so the user gets feedback instead of a silently-vanishing
  dialog; also guards remote folders with the same toast as the
  single-file path.
- _run_bulk_export / _bulk_convert_one: snapshot md_include_front_matter
  and odf_include_images once at batch start and pass them via an
  options dict, so a mid-batch toggle from another dialog can no longer
  produce a non-uniform batch.
- _bulk_convert_one (md branch): write to "<path>.tmp" and os.replace,
  matching the single-file atomic-write pattern.
- _bulk_export_worker: when fmt is not in _BULK_EXTENSIONS, close the
  dialog and toast a real export-failed message instead of falling
  back to a misleading "Saved 0 files".
- _build_progress_dialog: cancel handler now disables the button,
  swaps its label and AT-SPI accessible name to "Cancelling…", and
  rewrites the subtitle to "Finishing current step…". The progress
  callback short-circuits after cancel so the message doesn't get
  overwritten by late per-file updates. Gives the user immediate
  feedback while parse_tsv_pages finishes its current step on a long
  PDF.

Settings persistence (services/settings.py):

- Add _load_md_settings / _save_md_settings handling the
  md_export.include_front_matter and md_export.open_after_export
  config keys; hooked into load_settings / _save_all_settings.
- _update_md_setting (UI) now calls settings._save_md_settings()
  before config.save() so the Markdown toggles actually persist
  across restarts, matching the ODF flow.

Tests (test_markdown_export.py):

- TestEscapeMd.test_decimal_at_line_start_not_escaped: pins the new
  decimal-aware behavior; "1." alone still escapes via the end-of-
  string boundary.
- TestCreateMarkdown.test_kv_elements_separated_by_blank_line: pins
  the new KV separator rule.
- TestCreateMarkdown.test_paragraph_preserves_raw_lines: pins the new
  hard-break handling for multi-line OCR paragraphs.
- TestSaveMdSettings.{test_save_md_settings_writes_both_keys,
  test_load_md_settings_reads_both_keys,
  test_save_md_settings_defaults_when_unset}: cover the new persistence
  path end-to-end with a minimal config double.

364 passing tests, ruff clean.

Author: bigbruno

src/bigocrpdf/services/settings.py

@@ -142,6 +142,7 @@ def load_settings(self) -> None:
         self._load_date_settings()
         self._load_text_extraction_settings()
         self._load_odf_settings()
+        self._load_md_settings()
         self._load_preprocessing_settings()
         self._load_image_export_settings()
         self._load_pdf_output_settings()
@@ -197,6 +198,10 @@ def _load_odf_settings(self) -> None:
         self.odf_use_formatting = self._config.get("odf_export.use_formatting", True)
         self.odf_open_after_export = self._config.get("odf_export.open_after_export", False)
 
+    def _load_md_settings(self) -> None:
+        self.md_include_front_matter = self._config.get("md_export.include_front_matter", False)
+        self.md_open_after_export = self._config.get("md_export.open_after_export", False)
+
     def _load_preprocessing_settings(self) -> None:
         self.dpi = self._config.get("rapidocr.dpi", DEFAULT_DPI)
         self.enable_preprocessing = self._config.get(
@@ -473,6 +478,7 @@ def _save_all_settings(self) -> None:
         self._save_text_extraction_settings()
         self._save_editor_settings()
         self._save_odf_settings()
+        self._save_md_settings()
         self._save_preprocessing_settings()
         self._save_image_export_settings()
         self._save_pdf_output_settings()
@@ -536,6 +542,18 @@ def _save_odf_settings(self) -> None:
             "odf_export.open_after_export", self.odf_open_after_export, save_immediately=False
         )
 
+    def _save_md_settings(self) -> None:
+        self._config.set(
+            "md_export.include_front_matter",
+            getattr(self, "md_include_front_matter", False),
+            save_immediately=False,
+        )
+        self._config.set(
+            "md_export.open_after_export",
+            getattr(self, "md_open_after_export", False),
+            save_immediately=False,
+        )
+
     def _save_preprocessing_settings(self) -> None:
         self._config.set("rapidocr.dpi", self.dpi, save_immediately=False)
         self._config.set("rapidocr.language", self.ocr_language, save_immediately=False)
@@ -641,20 +659,26 @@ def get_pdf_suffix(self) -> str:
 
         # Add date elements with their preferred order
         if self.include_year:
-            date_components.append((
-                self.date_format_order.get("year", 1),
-                f"{now.tm_year}",
-            ))
+            date_components.append(
+                (
+                    self.date_format_order.get("year", 1),
+                    f"{now.tm_year}",
+                )
+            )
         if self.include_month:
-            date_components.append((
-                self.date_format_order.get("month", 2),
-                f"{now.tm_mon:02d}",
-            ))
+            date_components.append(
+                (
+                    self.date_format_order.get("month", 2),
+                    f"{now.tm_mon:02d}",
+                )
+            )
         if self.include_day:
-            date_components.append((
-                self.date_format_order.get("day", 3),
-                f"{now.tm_mday:02d}",
-            ))
+            date_components.append(
+                (
+                    self.date_format_order.get("day", 3),
+                    f"{now.tm_mday:02d}",
+                )
+            )
 
         # Sort components by their position value
         date_components.sort(key=lambda x: x[0])