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/stats.rs

@@ -3,6 +3,7 @@ use rusqlite::Connection;
 use serde::Serialize;
 
 use crate::Config;
+use crate::cli::robot::RobotMeta;
 use crate::core::db::create_connection;
 use crate::core::error::Result;
 use crate::core::paths::get_db_path;
@@ -441,9 +442,10 @@ pub fn print_stats(result: &StatsResult) {
 struct StatsJsonOutput {
     ok: bool,
     data: StatsResult,
+    meta: RobotMeta,
 }
 
-pub fn print_stats_json(result: &StatsResult) {
+pub fn print_stats_json(result: &StatsResult, elapsed_ms: u64) {
     let output = StatsJsonOutput {
         ok: true,
         data: StatsResult {
@@ -471,6 +473,7 @@ pub fn print_stats_json(result: &StatsResult) {
                 }),
             }),
         },
+        meta: RobotMeta { elapsed_ms },
     };
     println!("{}", serde_json::to_string(&output).unwrap());
 }