docs: overhaul documentation and add four new pages

- Add mining-workflow.md: end-to-end sentence mining guide
- Add anki-integration.md: AnkiConnect setup, field mapping, media generation, field grouping
- Add mpv-plugin.md: chord keybindings, subminer.conf options, script messages
- Add troubleshooting.md: common issues and solutions by category
- Rewrite architecture.md to reflect current ~1,400-line main.ts and ~35 services
- Expand development.md from ~25 lines to full dev guide
- Fix URLs to ksyasuda/SubMiner, version to v0.1.0, AppImage naming
- Update VitePress sidebar with three-group layout (Getting Started, Reference, Development)
- Update navigation in index.md, README.md, docs/README.md
- Remove obsolete planning artifacts (plan.md, investigation.md, comparison.md, composability.md, refactor-main-checklist.md)

docs/index.md

@@ -15,15 +15,15 @@ hero:
     - theme: brand
       text: Installation
       link: /installation
+    - theme: alt
+      text: Mining Workflow
+      link: /mining-workflow
     - theme: alt
       text: Configuration
       link: /configuration
     - theme: alt
-      text: Development
-      link: /development
-    - theme: alt
-      text: Architecture
-      link: /architecture
+      text: Troubleshooting
+      link: /troubleshooting
 
 features:
   - title: End-to-end workflow
@@ -33,11 +33,3 @@ features:
   - title: Contributor docs
     details: Build, test, and package SubMiner with the development notes in this docs set.
 ---
-
-<!-- ## Documentation Sections
-
-- [Installation](/installation)
-- [Usage](/usage)
-- [Configuration](/configuration)
-- [Development](/development)
-- [Architecture](/architecture) -->