Enable ty's unresolved-import rule

Broken first-party imports previously went undetected, since the rule was globally disabled to
accommodate optional extras and platform-specific modules. These are now handled narrowly:
per-file overrides for the agno integration (optional extra, not installed in CI) and for the
pywebview integration (several macOS-only imports), and an inline suppression for the single
macOS-only import in the dashboard.

pyproject.toml

@@ -114,10 +114,8 @@ python-version = "3.11"
 python-platform = "all"
 
 [tool.ty.rules]
-# Mirror mypy's ignore_missing_imports=true: optional extras (e.g. agno, google-genai) and
-# platform-specific modules (e.g. AppKit on macOS) are not installed in the default dev environment,
-# so we do not want unresolvable imports to fail the type check.
-unresolved-import = "ignore"
+# Unresolvable imports do fail the type check (catching broken first-party imports); the exceptions for
+# optional extras and platform-specific modules are handled per file/line below.
 possibly-missing-submodule = "ignore"
 
 [tool.ty.src]
@@ -127,6 +125,15 @@ possibly-missing-submodule = "ignore"
 # test/resources is instead excluded from the `ty check test` CLI task via its --exclude flag.
 exclude = ["build/", "docs/"]
 
+[[tool.ty.overrides]]
+# Modules whose imports cannot be resolved in the default dev environment: the agno integration depends
+# on the optional extra `agno`, and the pywebview integration imports macOS-only modules (AppKit, PyObjCTools)
+# in several places. Elsewhere, individual platform-specific imports are suppressed inline.
+include = ["src/serena/agno.py", "src/serena/util/pywebview.py"]
+
+[tool.ty.overrides.rules]
+unresolved-import = "ignore"
+
 [[tool.ty.overrides]]
 # Test code is heavily dynamic (pytest fixtures, MagicMock, intentionally loose Optionals). ty models
 # pytest's fail/skip helpers and MagicMock far more strictly than mypy did (mypy inferred `Any` for

src/serena/dashboard.py

@@ -1190,7 +1190,7 @@ class SerenaDashboardTrayManager:
         # set up tray icon with a dynamic menu (callable returns items on each open)
         kwargs: dict[str, Any] = {}
         if sys.platform == "darwin":
-            from AppKit import NSApplication, NSApplicationActivationPolicyAccessory
+            from AppKit import NSApplication, NSApplicationActivationPolicyAccessory  # ty: ignore[unresolved-import]  (macOS only)
 
             nsapp = NSApplication.sharedApplication()
             # run as an accessory app so that only the menu bar icon is shown (no Dock icon)