feat(blame): add file blame dialog with git porcelain parsing

This change introduces a new backend command to fetch file blame using
git's line-porcelain output and returns structured per-line metadata.
The UI adds a BlameDialog that groups lines by commit, highlights
uncommitted changes, and styles the dialog to match the updated theme.

- Add get_file_blame command and parsing with uncommitted detection
- Wire BlameDialog into the explorer file node actions
- Add blame UI component and supporting types and styles

.claude/settings.local.json

@@ -85,7 +85,14 @@
       "Bash(rustc --edition 2021 --crate-type bin -o /dev/null --emit=metadata src/main.rs)",
       "Bash(grep -B1 \"^error\\\\[E0432\\\\]\\\\|^error$\")",
       "Bash(grep -v \"^--$\")",
-      "Bash(grep \"^error$\" -A2)"
+      "Bash(grep \"^error$\" -A2)",
+      "Bash(cargo run *)",
+      "Bash(node_modules/.bin/svelte-check --version)",
+      "Bash(rustfmt --check --edition 2021 src/git.rs src/main.rs)",
+      "Bash(rustfmt --check --edition 2021 src/git.rs)",
+      "Bash(awk *)",
+      "Bash(rustfmt --edition 2021 /tmp/blame_chunk.rs)",
+      "Read(//tmp/**)"
     ]
   }
 }