fix(cli): JSON parity for /memory and /providers in resume mode

Two gaps closed:

1. /memory (resume): json field was None, emitting prose regardless of
   --output-format json. Now emits:
     {kind:memory, cwd, instruction_files:N, files:[{path,lines,preview}...]}

2. /providers (resume): had a spec entry but no parse arm, producing the
   circular 'Unknown slash command: /providers — Did you mean /providers'.
   Added 'providers' as an alias for 'doctor' in the parse match so
   /providers dispatches to the same structured diagnostic output.

3. /doctor (resume): also wired json_value() so --output-format json
   returns the structured doctor report instead of None.

Continues ROADMAP #26 resumed-command JSON parity track.
159 CLI tests pass, fmt clean.

rust/crates/commands/src/lib.rs

@@ -1320,7 +1320,7 @@ pub fn validate_slash_command_input(
         "skills" | "skill" => SlashCommand::Skills {
             args: parse_skills_args(remainder.as_deref())?,
         },
-        "doctor" => {
+        "doctor" | "providers" => {
             validate_no_args(command, &args)?;
             SlashCommand::Doctor
         }

rust/crates/rusty-claude-cli/src/main.rs

@@ -2773,7 +2773,7 @@ fn run_resume_command(
         SlashCommand::Memory => Ok(ResumeCommandOutcome {
             session: session.clone(),
             message: Some(render_memory_report()?),
-            json: None,
+            json: Some(render_memory_json()?),
         }),
         SlashCommand::Init => {
             let message = init_claude_md()?;
@@ -2829,11 +2829,14 @@ fn run_resume_command(
                 json: Some(handle_skills_slash_command_json(args.as_deref(), &cwd)?),
             })
         }
-        SlashCommand::Doctor => Ok(ResumeCommandOutcome {
+        SlashCommand::Doctor => {
-            session: session.clone(),
+            let report = render_doctor_report()?;
-            message: Some(render_doctor_report()?.render()),
+            Ok(ResumeCommandOutcome {
-            json: None,
+                session: session.clone(),
-        }),
+                message: Some(report.render()),
+                json: Some(report.json_value()),
+            })
+        }
         SlashCommand::Stats => {
             let usage = UsageTracker::from_session(session).cumulative_usage();
             Ok(ResumeCommandOutcome {
@@ -5421,6 +5424,28 @@ fn render_memory_report() -> Result<String, Box<dyn std::error::Error>> {
     ))
 }
 
+fn render_memory_json() -> Result<serde_json::Value, Box<dyn std::error::Error>> {
+    let cwd = env::current_dir()?;
+    let project_context = ProjectContext::discover(&cwd, DEFAULT_DATE)?;
+    let files: Vec<_> = project_context
+        .instruction_files
+        .iter()
+        .map(|f| {
+            json!({
+                "path": f.path.display().to_string(),
+                "lines": f.content.lines().count(),
+                "preview": f.content.lines().next().unwrap_or("").trim(),
+            })
+        })
+        .collect();
+    Ok(json!({
+        "kind": "memory",
+        "cwd": cwd.display().to_string(),
+        "instruction_files": files.len(),
+        "files": files,
+    }))
+}
+
 fn init_claude_md() -> Result<String, Box<dyn std::error::Error>> {
     let cwd = env::current_dir()?;
     Ok(initialize_repo(&cwd)?.render())