Fix Unicode space handling in macOS screenshot filenames

macOS uses U+202F (Narrow No-Break Space) in screenshot filenames
between the time and am/pm. When users type or paste these paths,
they use regular spaces, causing file-not-found errors.

Changes:
- Add resolve_path_with_unicode_fallback() to try U+202F variants
- Add resolve_paths_in_shell_command() for shell command paths
- Apply fix to read_file, read_image, and shell tools
- Fix read_image prompt docs: file_path -> file_paths (array)
- Add 6 unit tests for Unicode space normalization

crates/g3-core/src/tools/shell.rs

@@ -4,6 +4,7 @@ use anyhow::Result;
 use tracing::debug;
 
 use crate::ui_writer::UiWriter;
+use crate::utils::resolve_paths_in_shell_command;
 use crate::utils::shell_escape_command;
 use crate::ToolCall;
 
@@ -22,7 +23,10 @@ pub async fn execute_shell<W: UiWriter>(tool_call: &ToolCall, ctx: &ToolContext<
     };
     
     debug!("Command string: {}", command);
-    let escaped_command = shell_escape_command(command);
+    // First resolve any file paths with Unicode space fallback (macOS screenshot names)
+    let resolved_command = resolve_paths_in_shell_command(command);
+    debug!("Resolved command: {}", resolved_command);
+    let escaped_command = shell_escape_command(&resolved_command);
 
     let executor = g3_execution::CodeExecutor::new();