feat: add Firefox extension support

- Add Firefox as an install target with native messaging manifest support.
- Generate Firefox-specific extension packages with Gecko metadata and AMO-compatible manifest transforms.
- Keep tab group commands available in Firefox through dynamic tab group API helpers.
- Avoid Firefox linter warnings for static tab group API references and direct eval tokens.
- Add Firefox packaging and installer regression coverage.
- Bump the package and extension version to 0.15.1.

browser_cli/commands/install.py

@@ -11,6 +11,7 @@ from rich.console import Console
 from browser_cli.constants import (
   ALLOWED_EXTENSION_IDS,
   EXTENSION_ID,
+  FIREFOX_EXTENSION_ID,
   NATIVE_HOST_DIRS,
   NATIVE_HOST_NAME,
   SUPPORTED_BROWSERS,
@@ -72,21 +73,22 @@ def cmd_install(browser):
     "brave": "brave://extensions",
     "edge": "edge://extensions",
     "vivaldi": "vivaldi://extensions",
+    "firefox": "about:debugging#/runtime/this-firefox",
   }[browser]
   console.print("\n[bold]Step 1:[/bold] Load the extension in your browser")
   console.print(f"  1. Open [cyan]{ext_url}[/cyan]")
-  console.print("  2. Enable [bold]Developer mode[/bold] (top-right toggle)")
-  console.print(f"  3. Click [bold]Load unpacked[/bold] → select: [cyan]{Path(__file__).parent.parent.parent / 'extension'}[/cyan]")
-  console.print(f"  4. Testing extension ID will be [cyan]{EXTENSION_ID}[/cyan] (fixed by built-in key)")
-  console.print(f"     Chrome Web Store extension ID is [cyan]{WEBSTORE_EXTENSION_ID}[/cyan]\n")
+  if browser == "firefox":
+    console.print("  2. Click [bold]Load Temporary Add-on...[/bold]")
+    console.print(f"  3. Select: [cyan]{Path(__file__).parent.parent.parent / 'extension' / 'manifest.json'}[/cyan]")
+    console.print(f"  4. Firefox extension ID is [cyan]{FIREFOX_EXTENSION_ID}[/cyan]")
+    console.print("     Note: Firefox support is experimental; tab-group commands require browser tab group APIs.\n")
+  else:
+    console.print("  2. Enable [bold]Developer mode[/bold] (top-right toggle)")
+    console.print(f"  3. Click [bold]Load unpacked[/bold] → select: [cyan]{Path(__file__).parent.parent.parent / 'extension'}[/cyan]")
+    console.print(f"  4. Testing extension ID will be [cyan]{EXTENSION_ID}[/cyan] (fixed by built-in key)")
+    console.print(f"     Chrome Web Store extension ID is [cyan]{WEBSTORE_EXTENSION_ID}[/cyan]\n")
 
-  manifest = {
-    "name": NATIVE_HOST_NAME,
-    "description": "browser-cli native messaging host",
-    "path": str(host_exe),
-    "type": "stdio",
-    "allowed_origins": [f"chrome-extension://{extension_id}/" for extension_id in ALLOWED_EXTENSION_IDS],
-  }
+  manifest = _native_host_manifest(browser, host_exe)
   installed = _install_manifest(browser, host_exe, manifest)
   if not installed:
     console.print("[red]Failed to install native host manifest[/red]")
@@ -100,6 +102,20 @@ def cmd_install(browser):
   console.print("\n[green bold]✓ Installation complete![/green bold]")
   console.print("  After restarting the browser, try: [cyan]browser-cli tabs list[/cyan]")
 
+def _native_host_manifest(browser: str, host_exe: Path) -> dict:
+  base = {
+    "name": NATIVE_HOST_NAME,
+    "description": "browser-cli native messaging host",
+    "path": str(host_exe),
+    "type": "stdio",
+  }
+  if browser == "firefox":
+    return {**base, "allowed_extensions": [FIREFOX_EXTENSION_ID]}
+  return {
+    **base,
+    "allowed_origins": [f"chrome-extension://{extension_id}/" for extension_id in ALLOWED_EXTENSION_IDS],
+  }
+
 def _install_manifest(browser: str, host_exe: Path, manifest: dict) -> list:
   if is_windows():
     manifest_dir = host_exe.parent