feat(copilot): CLI native integration

docs/guide/getting-started/supported-agents.md

@@ -30,7 +30,7 @@ Agent runs "cargo test"
 |-------|-----------------|---------------------------|
 | Claude Code | Shell hook (`PreToolUse`) | Yes |
 | VS Code Copilot Chat | Shell hook (`PreToolUse`) | Yes |
-| GitHub Copilot CLI | Shell hook (deny-with-suggestion) | No (agent retries) |
+| GitHub Copilot CLI | Shell hook (`preToolUse` `modifiedArgs`) | Yes |
 | Cursor | Shell hook (`preToolUse`) | Yes |
 | Gemini CLI | Rust binary (`BeforeTool`) | Yes |
 | OpenCode | TypeScript plugin (`tool.execute.before`) | Yes |
@@ -66,12 +66,24 @@ rtk init --global --cursor
 
 Restart Cursor. The hook uses `preToolUse` with Cursor's `updated_input` format.
 
-### VS Code Copilot Chat
+### GitHub Copilot (VS Code Chat + CLI)
 
 ```bash
-rtk init --global --copilot
+rtk init --copilot            # project-scoped (.github/hooks/)
+rtk init --global --copilot   # user-scoped (~/.copilot/hooks/, respects $COPILOT_HOME)
 ```
 
+Project-scoped writes `.github/hooks/rtk-rewrite.json` (both hosts get transparent rewrite — VS Code Chat via `updatedInput`, Copilot CLI via `modifiedArgs`) plus the RTK block in `.github/copilot-instructions.md`. User-scoped writes the same hook config to `~/.copilot/hooks/rtk-rewrite.json` and the RTK block to `~/.copilot/copilot-instructions.md` (both respect `$COPILOT_HOME` if set).
+
+Uninstall:
+
+```bash
+rtk init --uninstall --copilot
+rtk init --uninstall --global --copilot
+```
+
+Removes only RTK's hook file (and, for project, the RTK block in `copilot-instructions.md`). Other files in `.github/hooks/` or `~/.copilot/hooks/` and your own instruction content are untouched.
+
 ### Gemini CLI
 
 ```bash

src/core/telemetry.rs

@@ -368,11 +368,14 @@ fn detect_hook_type() -> String {
         }
     }
 
-    // Check project-level hooks
+    // Check project-level hooks (Claude script + project-scoped Copilot config)
     if let Ok(cwd) = std::env::current_dir() {
         if cwd.join(".claude/hooks/rtk-rewrite.sh").exists() {
             return "claude".to_string();
         }
+        if cwd.join(".github/hooks/rtk-rewrite.json").exists() {
+            return "copilot".to_string();
+        }
     }
 
     "none".to_string()
@@ -571,7 +574,7 @@ mod tests {
         assert!(stats.low_savings_commands.len() <= 5);
         assert!((0.0..=100.0).contains(&stats.avg_savings_per_command));
         assert!(
-            ["claude", "gemini", "codex", "cursor", "none", "unknown"]
+            ["claude", "gemini", "codex", "cursor", "copilot", "none", "unknown"]
                 .iter()
                 .any(|&h| stats.hook_type.starts_with(h)),
             "Unexpected hook type: {}",
@@ -583,7 +586,8 @@ mod tests {
     fn test_detect_hook_type_returns_known() {
         let ht = detect_hook_type();
         assert!(
-            ["claude", "gemini", "codex", "cursor", "none", "unknown"].contains(&ht.as_str()),
+            ["claude", "gemini", "codex", "cursor", "copilot", "none", "unknown"]
+                .contains(&ht.as_str()),
             "Unexpected hook type: {}",
             ht
         );

src/discover/report.rs

@@ -1,8 +1,8 @@
 //! Data types for reporting which commands RTK can and cannot optimize.
 
 use crate::hooks::constants::{
-    CURSOR_DIR, HERMES_DIR, HERMES_PLUGINS_SUBDIR, HERMES_PLUGIN_MANIFEST_FILE, HERMES_PLUGIN_NAME,
-    HOOKS_SUBDIR, REWRITE_HOOK_FILE,
+    COPILOT_HOOK_FILE, CURSOR_DIR, GITHUB_DIR, HERMES_DIR, HERMES_PLUGINS_SUBDIR,
+    HERMES_PLUGIN_MANIFEST_FILE, HERMES_PLUGIN_NAME, HOOKS_SUBDIR, REWRITE_HOOK_FILE,
 };
 use serde::Serialize;
 use std::path::Path;
@@ -52,13 +52,19 @@ pub struct UnsupportedEntry {
 pub struct AgentIntegrationStatus {
     pub cursor_hook_installed: bool,
     pub hermes_plugin_installed: bool,
+    pub copilot_hook_installed: bool,
 }
 
 impl AgentIntegrationStatus {
     pub fn detect() -> Self {
-        dirs::home_dir()
+        let mut status = dirs::home_dir()
             .map(|home| Self::detect_from_home(&home))
-            .unwrap_or_default()
+            .unwrap_or_default();
+        // Copilot is project-scoped (.github/hooks/), unlike the home-based agents.
+        status.copilot_hook_installed = std::env::current_dir()
+            .map(|cwd| Self::copilot_hook_installed_in(&cwd))
+            .unwrap_or(false);
+        status
     }
 
     fn detect_from_home(home: &Path) -> Self {
@@ -74,8 +80,16 @@ impl AgentIntegrationStatus {
                 .join(HERMES_PLUGIN_NAME)
                 .join(HERMES_PLUGIN_MANIFEST_FILE)
                 .is_file(),
+            copilot_hook_installed: false,
         }
     }
+
+    fn copilot_hook_installed_in(dir: &Path) -> bool {
+        dir.join(GITHUB_DIR)
+            .join(HOOKS_SUBDIR)
+            .join(COPILOT_HOOK_FILE)
+            .exists()
+    }
 }
 
 /// Full discover report.
@@ -221,6 +235,10 @@ fn append_agent_notes(out: &mut String, status: AgentIntegrationStatus) {
     if status.hermes_plugin_installed {
         out.push_str("\nNote: Hermes plugin is installed; Hermes sessions are tracked via `rtk gain` (discover scans Claude Code only)\n");
     }
+
+    if status.copilot_hook_installed {
+        out.push_str("\nNote: GitHub Copilot sessions are tracked via `rtk gain` (discover scans Claude Code only)\n");
+    }
 }
 
 /// Format report as JSON.
@@ -362,12 +380,50 @@ mod tests {
         report.agent_status = AgentIntegrationStatus {
             cursor_hook_installed: true,
             hermes_plugin_installed: true,
+            copilot_hook_installed: true,
         };
 
         let output = format_json(&report);
         let json: serde_json::Value = serde_json::from_str(&output).unwrap();
 
         assert_eq!(json["agent_status"]["cursor_hook_installed"], true);
         assert_eq!(json["agent_status"]["hermes_plugin_installed"], true);
+        assert_eq!(json["agent_status"]["copilot_hook_installed"], true);
+    }
+
+    #[test]
+    fn test_agent_status_detects_copilot_hook_in_project() {
+        let temp = tempfile::tempdir().unwrap();
+        let hook = temp
+            .path()
+            .join(GITHUB_DIR)
+            .join(HOOKS_SUBDIR)
+            .join(COPILOT_HOOK_FILE);
+        std::fs::create_dir_all(hook.parent().unwrap()).unwrap();
+        std::fs::write(&hook, "{}").unwrap();
+
+        assert!(AgentIntegrationStatus::copilot_hook_installed_in(
+            temp.path()
+        ));
+        assert!(!AgentIntegrationStatus::copilot_hook_installed_in(
+            tempfile::tempdir().unwrap().path()
+        ));
+    }
+
+    #[test]
+    fn test_format_text_reports_copilot_detected() {
+        let mut report = make_report(0, 0);
+        report.agent_status = AgentIntegrationStatus {
+            copilot_hook_installed: true,
+            ..AgentIntegrationStatus::default()
+        };
+
+        let output = format_text(&report, 10, false);
+
+        assert!(
+            output.contains("GitHub Copilot sessions are tracked via `rtk gain`"),
+            "Expected Copilot note in output but got:\n{}",
+            output
+        );
     }
 }

src/hooks/constants.rs

@@ -22,6 +22,12 @@ pub const CURSOR_DIR: &str = ".cursor";
 pub const CODEX_DIR: &str = ".codex";
 pub const GEMINI_DIR: &str = ".gemini";
 
+pub const GITHUB_DIR: &str = ".github";
+pub const COPILOT_HOOK_FILE: &str = "rtk-rewrite.json";
+pub const COPILOT_INSTRUCTIONS_FILE: &str = "copilot-instructions.md";
+pub const COPILOT_USER_DIR: &str = ".copilot";
+pub const COPILOT_HOME_ENV: &str = "COPILOT_HOME";
+
 pub const PI_DIR: &str = ".pi/agent";
 pub const PI_LOCAL_DIR: &str = ".pi";
 pub const PI_EXTENSIONS_SUBDIR: &str = "extensions";