feat(robot): add elapsed_ms timing, --fields support, and actionable error actions

Robot mode consistency improvements across all command output:

Timing:
- Every robot JSON response now includes meta.elapsed_ms measuring
  wall-clock time from command start to serialization. Agents can use
  this to detect slow queries and tune --limit or --project filters.

Field selection (--fields):
- print_list_issues_json and print_list_mrs_json accept an optional
  fields slice that prunes each item in the response array to only
  the requested keys. A "minimal" preset expands to
  [iid, title, state, updated_at_iso] for token-efficient agent scans.
- filter_fields and expand_fields_preset live in the new
  src/cli/robot.rs module alongside RobotMeta.

Actionable error recovery:
- LoreError gains an actions() method returning concrete shell commands
  an agent can execute to recover (e.g. "ollama serve" for
  OllamaUnavailable, "lore init" for ConfigNotFound).
- RobotError now serializes an "actions" array (empty array omitted)
  so agents can parse and offer one-click fixes.

Envelope consistency:
- show issue/MR JSON responses now use the standard
  {"ok":true,"data":...,"meta":...} envelope instead of bare data,
  matching all other commands.

Files: src/cli/robot.rs (new), src/core/error.rs,
       src/cli/commands/{count,embed,generate_docs,ingest,list,show,stats,sync_status}.rs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/cli/commands/list.rs

@@ -3,6 +3,7 @@ use rusqlite::Connection;
 use serde::Serialize;
 
 use crate::Config;
+use crate::cli::robot::{RobotMeta, expand_fields_preset, filter_fields};
 use crate::core::db::create_connection;
 use crate::core::error::{LoreError, Result};
 use crate::core::paths::get_db_path;
@@ -734,9 +735,20 @@ pub fn print_list_issues(result: &ListResult) {
     println!("{table}");
 }
 
-pub fn print_list_issues_json(result: &ListResult) {
+pub fn print_list_issues_json(result: &ListResult, elapsed_ms: u64, fields: Option<&[String]>) {
     let json_result = ListResultJson::from(result);
-    match serde_json::to_string_pretty(&json_result) {
+    let meta = RobotMeta { elapsed_ms };
+    let output = serde_json::json!({
+        "ok": true,
+        "data": json_result,
+        "meta": meta,
+    });
+    let mut output = output;
+    if let Some(f) = fields {
+        let expanded = expand_fields_preset(f, "issues");
+        filter_fields(&mut output, "issues", &expanded);
+    }
+    match serde_json::to_string(&output) {
         Ok(json) => println!("{json}"),
         Err(e) => eprintln!("Error serializing to JSON: {e}"),
     }
@@ -819,9 +831,20 @@ pub fn print_list_mrs(result: &MrListResult) {
     println!("{table}");
 }
 
-pub fn print_list_mrs_json(result: &MrListResult) {
+pub fn print_list_mrs_json(result: &MrListResult, elapsed_ms: u64, fields: Option<&[String]>) {
     let json_result = MrListResultJson::from(result);
-    match serde_json::to_string_pretty(&json_result) {
+    let meta = RobotMeta { elapsed_ms };
+    let output = serde_json::json!({
+        "ok": true,
+        "data": json_result,
+        "meta": meta,
+    });
+    let mut output = output;
+    if let Some(f) = fields {
+        let expanded = expand_fields_preset(f, "mrs");
+        filter_fields(&mut output, "mrs", &expanded);
+    }
+    match serde_json::to_string(&output) {
         Ok(json) => println!("{json}"),
         Err(e) => eprintln!("Error serializing to JSON: {e}"),
     }