refactor: remove bundled Claude Code binary support

- Remove all bundled/sidecar binary functionality
- Delete build scripts for fetching and building Claude executables
- Simplify binary detection to only support system installations
- Update UI to remove bundled installation options
- Update build configuration and documentation

src-tauri/capabilities/default.json

@@ -14,11 +14,6 @@
     {
       "identifier": "shell:allow-execute",
       "allow": [
-        {
-          "name": "claude-code",
-          "sidecar": true,
-          "args": true
-        },
         {
           "name": "claude",
           "sidecar": false,
@@ -29,11 +24,6 @@
     {
       "identifier": "shell:allow-spawn",
       "allow": [
-        {
-          "name": "claude-code",
-          "sidecar": true,
-          "args": true
-        },
         {
           "name": "claude",
           "sidecar": false,