feat: phase 2 quick wins (#65 #69 #72)

- #65: update policies + per-agent version pinning
  - add settings.update_policy (stable/latest/skip)
  - add AgentDef.pin_version
  - honor both in update_cmd
  - add update_policy tests

- #69: REPL color theme CLI command
  - add am theme [name] (show/switch)
  - persist selected theme to config

- #72: doctor checks local model runtimes
  - verify ollama and llama-server on PATH
  - for ollama, also check server responds (ollama ls)

Version 0.4.4

src/commands/mod.rs

@@ -28,6 +28,7 @@ pub mod sessions_cmd;
 pub mod stats_cmd;
 pub mod self_update;
 pub mod status_cmd;
+pub mod theme_cmd;
 pub mod timeline_cmd;
 pub mod tip_cmd;
 pub mod uninstall_cmd;
@@ -37,7 +38,7 @@ pub mod version_cmd;
 
 use crate::app::App;
 use crate::cli::Command;
-use crate::config::{AgentDef, MethodSpec};
+use crate::config::{AgentDef, MethodSpec, UpdatePolicy};
 use crate::state::InstalledEntry;
 use anyhow::{anyhow, bail, Result};
 use std::collections::BTreeMap;
@@ -164,6 +165,7 @@ pub fn execute_command(app: &App, cmd: &Command) -> Result<i32> {
         Command::Version => version_cmd::run(app),
         Command::Tip { random } => tip_cmd::run(app, *random),
         Command::Config(sub) => config_cmd::run(app, sub),
+        Command::Theme { name } => theme_cmd::run(app, name.as_deref()),
         Command::Doctor { fix } => doctor_cmd::run(app, *fix),
         Command::Run { agent, args } => run_cmd::run(app, agent, args),
         Command::Completion { shell, installed } => completion_cmd::run(*shell, *installed),

src/commands/theme_cmd.rs

@@ -0,0 +1,41 @@
+//! theme: switch the active color theme and persist it for the next start.
+//!
+//! With no argument, prints the current theme and the available list.
+//! With a name, switches to that theme (also used by the REPL 'theme' command).
+
+use super::*;
+use crate::theme;
+
+pub fn run(app: &App, name: Option<&str>) -> Result<i32> {
+    if let Some(name) = name {
+        let theme = theme::find(name).ok_or_else(|| {
+            anyhow::anyhow!(
+                "unknown theme '{name}' — available: {}",
+                theme::names().join(", ")
+            )
+        })?;
+        app.set_theme(theme);
+        crate::commands::config_cmd::persist_setting(app, "settings.theme", theme.name)?;
+        app.log.success(&format!(
+            "theme set to {} ({})",
+            theme.name,
+            theme.title
+        ));
+        return Ok(0);
+    }
+
+    // No argument: show current and list.
+    let current = app.theme();
+    if app.json() {
+        crate::output::print_json(&serde_json::json!({
+            "current": current.name,
+            "title": current.title,
+            "available": theme::names(),
+        }));
+    } else {
+        println!("current theme: {} — {}", current.name, current.title);
+        println!("available themes: {}", theme::names().join(", "));
+        println!("use 'am theme <name>' to switch");
+    }
+    Ok(0)
+}

src/commands/update_cmd.rs

@@ -11,7 +11,17 @@ use std::path::PathBuf;
 
 pub fn run(app: &App, agent_name: Option<&str>, all: bool) -> Result<i32> {
     let runner = SystemRunner::new(app.dry_run(), app.cli.verbose, &app.log);
+
+    let policy = app.config.settings.update_policy.unwrap_or_default();
+    if policy == UpdatePolicy::None && all {
+        app.log.warn("update policy is 'none'; 'am update --all' is a no-op");
+        return Ok(0);
+    }
+
     if let Some(name) = agent_name {
+        if policy == UpdatePolicy::None && !app.yes() {
+            app.log.warn("update policy is 'none'; use --yes to force a single-agent update");
+        }
         return update_one(app, &runner, name);
     }
     if all {
@@ -31,6 +41,30 @@ pub fn run(app: &App, agent_name: Option<&str>, all: bool) -> Result<i32> {
 
 fn update_one(app: &App, runner: &dyn Runner, name: &str) -> Result<i32> {
     let agent = require_agent(app, name)?;
+
+    // Issue #65: honor per-agent pinned version.
+    if let Some(pin) = agent.pin_version.as_deref() {
+        let current = app
+            .state
+            .get(&agent.name)
+            .ok()
+            .flatten()
+            .and_then(|e| e.version.clone());
+        if current.as_deref() == Some(pin) {
+            app.log.success(&format!(
+                "{} is pinned to v{pin} and already at that version",
+                agent.title()
+            ));
+        } else {
+            app.log.warn(&format!(
+                "{} is pinned to v{pin} but currently at {}; update skipped",
+                agent.title(),
+                current.as_deref().unwrap_or("unknown")
+            ));
+        }
+        return Ok(0);
+    }
+
     let Some(entry) = app.state.get(&agent.name).ok().flatten() else {
         bail!(
             "agent '{}' is not installed by agent-manager — use 'am install {}'",