feat(cli): Add global robot mode for machine-readable output

Introduces a unified robot mode that enables JSON output across all
commands, designed for AI agent and script consumption.

Robot mode activation (any of):
- --robot flag: Explicit opt-in
- GI_ROBOT=1 env var: For persistent configuration
- Non-TTY stdout: Auto-detect when piped (e.g., gi list issues | jq)

Implementation:
- Cli::is_robot_mode(): Centralized detection logic
- All command handlers receive robot_mode boolean
- Errors emit structured JSON to stderr with exit codes
- Success responses emit JSON to stdout

Behavior changes in robot mode:
- No color/emoji output (no ANSI escapes)
- No progress spinners or interactive prompts
- Timestamps as ISO 8601 strings (not relative "2 hours ago")
- Full content (no truncation of descriptions/notes)
- Structured error objects with code, message, suggestion

This enables reliable parsing by Claude Code, shell scripts, and
automation pipelines. The auto-detect on non-TTY means simple piping
"just works" without explicit flags.

Per-command --json flags remain for explicit control and override
robot mode when needed for human-friendly terminal + JSON file output.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/cli/mod.rs

@@ -3,6 +3,7 @@
 pub mod commands;
 
 use clap::{Parser, Subcommand};
+use std::io::IsTerminal;
 
 /// GitLab Inbox - Unified notification management
 #[derive(Parser)]
@@ -13,11 +14,23 @@ pub struct Cli {
     #[arg(short, long, global = true)]
     pub config: Option<String>,
 
+    /// Machine-readable JSON output (auto-enabled when piped)
+    #[arg(long, global = true, env = "GI_ROBOT")]
+    pub robot: bool,
+
     #[command(subcommand)]
     pub command: Commands,
 }
 
+impl Cli {
+    /// Check if robot mode is active (explicit flag, env var, or non-TTY stdout)
+    pub fn is_robot_mode(&self) -> bool {
+        self.robot || !std::io::stdout().is_terminal()
+    }
+}
+
 #[derive(Subcommand)]
+#[allow(clippy::large_enum_variant)]
 pub enum Commands {
     /// Initialize configuration and database
     Init {
@@ -62,7 +75,7 @@ pub enum Commands {
     /// Ingest data from GitLab
     Ingest {
         /// Resource type to ingest
-        #[arg(long, value_parser = ["issues", "merge_requests"])]
+        #[arg(long, value_parser = ["issues", "mrs"])]
         r#type: String,
 
         /// Filter to single project
@@ -92,8 +105,8 @@ pub enum Commands {
         #[arg(long)]
         project: Option<String>,
 
-        /// Filter by state
-        #[arg(long, value_parser = ["opened", "closed", "all"])]
+        /// Filter by state (opened|closed|all for issues; opened|merged|closed|locked|all for MRs)
+        #[arg(long)]
         state: Option<String>,
 
         /// Filter by author username
@@ -108,7 +121,7 @@ pub enum Commands {
         #[arg(long)]
         label: Option<Vec<String>>,
 
-        /// Filter by milestone title
+        /// Filter by milestone title (issues only)
         #[arg(long)]
         milestone: Option<String>,
 
@@ -116,11 +129,11 @@ pub enum Commands {
         #[arg(long)]
         since: Option<String>,
 
-        /// Filter by due date (before this date, YYYY-MM-DD)
+        /// Filter by due date (before this date, YYYY-MM-DD) (issues only)
         #[arg(long)]
         due_before: Option<String>,
 
-        /// Show only issues with a due date
+        /// Show only issues with a due date (issues only)
         #[arg(long)]
         has_due_date: bool,
 
@@ -132,13 +145,33 @@ pub enum Commands {
         #[arg(long, value_parser = ["desc", "asc"], default_value = "desc")]
         order: String,
 
-        /// Open first matching issue in browser
+        /// Open first matching item in browser
         #[arg(long)]
         open: bool,
 
         /// Output as JSON
         #[arg(long)]
         json: bool,
+
+        /// Show only draft MRs (MRs only)
+        #[arg(long, conflicts_with = "no_draft")]
+        draft: bool,
+
+        /// Exclude draft MRs (MRs only)
+        #[arg(long, conflicts_with = "draft")]
+        no_draft: bool,
+
+        /// Filter by reviewer username (MRs only)
+        #[arg(long)]
+        reviewer: Option<String>,
+
+        /// Filter by target branch (MRs only)
+        #[arg(long)]
+        target_branch: Option<String>,
+
+        /// Filter by source branch (MRs only)
+        #[arg(long)]
+        source_branch: Option<String>,
     },
 
     /// Count entities in local database
@@ -164,5 +197,9 @@ pub enum Commands {
         /// Filter by project path (required if iid is ambiguous)
         #[arg(long)]
         project: Option<String>,
+
+        /// Output as JSON
+        #[arg(long)]
+        json: bool,
     },
 }