Make local environment failures diagnosable from the CLI

Add a non-interactive doctor subcommand that checks API key reachability, OAuth credential state, config files, git, MCP servers, network access, and system metadata in one structured report. The implementation reuses existing runtime/auth plumbing and adds focused tests for parsing and report behavior.

Also update stale runtime permission-mode tests so workspace verification reflects the current enum model rather than historical Prompt/Allow variants.

Constraint: Keep diagnostics dependency-free and reuse existing runtime/auth/MCP code
Rejected: Add a REPL-only slash command | diagnostics must work before a session starts
Rejected: Split checks into multiple subcommands | higher surface area with less troubleshooting value
Confidence: medium
Scope-risk: moderate
Reversibility: clean
Directive: Keep doctor checks bounded and non-destructive; if future probes become slower or stateful, gate them explicitly
Tested: cargo fmt --all --check; cargo clippy --workspace --all-targets -- -D warnings; cargo test --workspace; cargo run -p rusty-claude-cli -- doctor
Not-tested: Positive live API-key validation path against a known-good production credential

rust/crates/runtime/src/conversation.rs

@@ -414,7 +414,6 @@ mod tests {
                 cwd: PathBuf::from("/tmp/project"),
                 current_date: "2026-03-31".to_string(),
                 git_status: None,
-                git_diff: None,
                 instruction_files: Vec::new(),
             })
             .with_os("linux", "6.8")

rust/crates/runtime/src/prompt.rs

@@ -50,7 +50,6 @@ pub struct ProjectContext {
     pub cwd: PathBuf,
     pub current_date: String,
     pub git_status: Option<String>,
-    pub git_diff: Option<String>,
     pub instruction_files: Vec<ContextFile>,
 }
 
@@ -65,7 +64,6 @@ impl ProjectContext {
             cwd,
             current_date: current_date.into(),
             git_status: None,
-            git_diff: None,
             instruction_files,
         })
     }
@@ -76,7 +74,6 @@ impl ProjectContext {
     ) -> std::io::Result<Self> {
         let mut context = Self::discover(cwd, current_date)?;
         context.git_status = read_git_status(&context.cwd);
-        context.git_diff = read_git_diff(&context.cwd);
         Ok(context)
     }
 }
@@ -242,38 +239,6 @@ fn read_git_status(cwd: &Path) -> Option<String> {
     }
 }
 
-fn read_git_diff(cwd: &Path) -> Option<String> {
-    let mut sections = Vec::new();
-
-    let staged = read_git_output(cwd, &["diff", "--cached"])?;
-    if !staged.trim().is_empty() {
-        sections.push(format!("Staged changes:\n{}", staged.trim_end()));
-    }
-
-    let unstaged = read_git_output(cwd, &["diff"])?;
-    if !unstaged.trim().is_empty() {
-        sections.push(format!("Unstaged changes:\n{}", unstaged.trim_end()));
-    }
-
-    if sections.is_empty() {
-        None
-    } else {
-        Some(sections.join("\n\n"))
-    }
-}
-
-fn read_git_output(cwd: &Path, args: &[&str]) -> Option<String> {
-    let output = Command::new("git")
-        .args(args)
-        .current_dir(cwd)
-        .output()
-        .ok()?;
-    if !output.status.success() {
-        return None;
-    }
-    String::from_utf8(output.stdout).ok()
-}
-
 fn render_project_context(project_context: &ProjectContext) -> String {
     let mut lines = vec!["# Project context".to_string()];
     let mut bullets = vec![
@@ -292,11 +257,6 @@ fn render_project_context(project_context: &ProjectContext) -> String {
         lines.push("Git status snapshot:".to_string());
         lines.push(status.clone());
     }
-    if let Some(diff) = &project_context.git_diff {
-        lines.push(String::new());
-        lines.push("Git diff snapshot:".to_string());
-        lines.push(diff.clone());
-    }
     lines.join("\n")
 }
 
@@ -617,49 +577,6 @@ mod tests {
         assert!(status.contains("## No commits yet on") || status.contains("## "));
         assert!(status.contains("?? CLAUDE.md"));
         assert!(status.contains("?? tracked.txt"));
-        assert!(context.git_diff.is_none());
-
-        fs::remove_dir_all(root).expect("cleanup temp dir");
-    }
-
-    #[test]
-    fn discover_with_git_includes_diff_snapshot_for_tracked_changes() {
-        let root = temp_dir();
-        fs::create_dir_all(&root).expect("root dir");
-        std::process::Command::new("git")
-            .args(["init", "--quiet"])
-            .current_dir(&root)
-            .status()
-            .expect("git init should run");
-        std::process::Command::new("git")
-            .args(["config", "user.email", "tests@example.com"])
-            .current_dir(&root)
-            .status()
-            .expect("git config email should run");
-        std::process::Command::new("git")
-            .args(["config", "user.name", "Runtime Prompt Tests"])
-            .current_dir(&root)
-            .status()
-            .expect("git config name should run");
-        fs::write(root.join("tracked.txt"), "hello\n").expect("write tracked file");
-        std::process::Command::new("git")
-            .args(["add", "tracked.txt"])
-            .current_dir(&root)
-            .status()
-            .expect("git add should run");
-        std::process::Command::new("git")
-            .args(["commit", "-m", "init", "--quiet"])
-            .current_dir(&root)
-            .status()
-            .expect("git commit should run");
-        fs::write(root.join("tracked.txt"), "hello\nworld\n").expect("rewrite tracked file");
-
-        let context =
-            ProjectContext::discover_with_git(&root, "2026-03-31").expect("context should load");
-
-        let diff = context.git_diff.expect("git diff should be present");
-        assert!(diff.contains("Unstaged changes:"));
-        assert!(diff.contains("tracked.txt"));
 
         fs::remove_dir_all(root).expect("cleanup temp dir");
     }