ATC: M100..M103 preprocessor + Mach MDI rewrite + hook handlers

ATC pneumatics in g-code (drop tool / grab tool / release clamp /
engage clamp) are expressed as M100..M103. AuxPreprocessor rewrites
those into (MSG,HOOK:droptool:) etc on file upload + on planner
load + on MDI input, so the Hooks layer (B1) can dispatch them via
registered ATC handlers in Ctrl.

- AuxPreprocessor.py: regex-based file rewriter, idempotent.
- FileHandler: invoke preprocessor on every upload.
- Planner.init: also re-preprocess on load (catches files written
  before this version).
- Mach.mdi: same rewrite for ad-hoc MDI input so M101 typed at the
  console produces a HOOK message.
- Ctrl: register the four ATC hooks (droptool/grabtool/release/clamp)
  with block_unpause + auto_resume so programs using them pause at
  the right point and resume cleanly. aux_home retained as a legacy
  alias for older preprocessed files.

src/py/bbctrl/Ctrl.py

@@ -88,6 +88,7 @@ class Ctrl(object):
                 # mirrors into State after homing.
                 self.aux.set_state_observer(
                     self.ext_axis.refresh_homed)
+            self._register_aux_hooks()
 
             with Trace.span('ctrl.mach.connect'):
                 self.mach.connect()
@@ -144,12 +145,61 @@ class Ctrl(object):
         self.preplanner.start()
 
 
+    def _register_aux_hooks(self):
+        """Wire up auxcnc HOOK: events to AuxAxis methods.
+
+        v2: motion hooks (aux/aux_rel/aux_home/aux_setzero) are
+        retired now that the W axis is integrated through gplan as
+        a virtual A axis (see ExternalAxis). Only the ATC pneumatic
+        hooks remain - those are events, not motion.
+
+        For backwards compatibility with files that still contain
+        (MSG,HOOK:aux_home:) (e.g. older preprocessed gcode), keep
+        an aux_home alias that routes to the standard ext_axis homing
+        path."""
+        log = self.log.get('AuxAxis')
+
+        def _hook_aux_home(ctx):
+            # Legacy: route to the standard external-axis homing.
+            if self.ext_axis is not None and self.ext_axis.enabled:
+                self.ext_axis.home()
+            else:
+                self.aux.home()
+
+        def _hook_droptool(ctx):  self.aux.atc_droptool()
+        def _hook_grabtool(ctx):  self.aux.atc_grabtool()
+        def _hook_release(ctx):   self.aux.atc_release()
+        def _hook_clamp(ctx):     self.aux.atc_clamp()
+
+        # Legacy alias for older gcode that used aux_home.
+        self.hooks.register_internal('aux_home',    _hook_aux_home,
+                                     block_unpause=True, auto_resume=True,
+                                     timeout=180)
+
+        # ATC pneumatics. block_unpause + auto_resume so a program
+        # using M100/M101/M102/M103 pauses at the right point and
+        # resumes once the sequence is done.
+        self.hooks.register_internal('droptool',    _hook_droptool,
+                                     block_unpause=True, auto_resume=True,
+                                     timeout=60)
+        self.hooks.register_internal('grabtool',    _hook_grabtool,
+                                     block_unpause=True, auto_resume=True,
+                                     timeout=60)
+        self.hooks.register_internal('release',     _hook_release,
+                                     block_unpause=True, auto_resume=True,
+                                     timeout=10)
+        self.hooks.register_internal('clamp',       _hook_clamp,
+                                     block_unpause=True, auto_resume=True,
+                                     timeout=15)
+        log.info('Aux hooks registered')
+
+
     def close(self):
-        try: self.ext_axis.close()
-        except Exception: pass
-        try: self.aux.close()
-        except Exception: pass
         self.log.get('Ctrl').info('Closing %s' % self.id)
         self.ioloop.close()
         self.avr.close()
         self.mach.planner.close()
+        try: self.ext_axis.close()
+        except Exception: pass
+        try: self.aux.close()
+        except Exception: pass