refactor(jobs): address code review feedback on fp.job.step (Task 1.5)

- I2: Add TODO comment block + stub button_pause/button_skip/
  button_cancel that raise NotImplementedError. Makes the missing
  state-machine paths explicit instead of invisible gaps. Future
  Task 1.6 wires the real implementations; shop-floor buttons in
  Task 1.8 can already point to the right method names.
- I3: button_finish now preserves first-finish audit timestamp
  via 'if not step.date_finished:' guard, mirroring button_start.
  Future rework flow that re-opens a step won't lose the original
  finish data. The duration_actual rollup landing in Task 1.7 will
  use timelog rows for the most-recent interval if needed.
- I4: step_count and step_done_count are now store=True so list
  views and stat buttons (Task 1.8) don't recompute across all
  job rows on every render. step_progress_pct and current_step_id
  stay non-stored - they're cheap derivatives. Split compute methods
  so stored + non-stored fields don't share one method (Odoo flags
  the mix as inconsistent and recomputes stored fields whenever the
  non-stored one is read, defeating the perf gain).

Manifest 19.0.8.4.0 -> 19.0.8.4.1.

Part of: native job model migration (spec 2026-04-25)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

fusion_plating/fusion_plating/__manifest__.py

@@ -5,7 +5,7 @@
 
 {
     'name': 'Fusion Plating',
-    'version': '19.0.8.4.0',
+    'version': '19.0.8.4.1',
     'category': 'Manufacturing/Plating',
     'summary': 'Core plating / metal finishing ERP: facilities, processes, tanks, baths, jobs, operators.',
     'description': """

fusion_plating/fusion_plating/models/fp_job.py

@@ -186,9 +186,14 @@ class FpJob(models.Model):
         'job_id',
         string='Steps',
     )
-    step_count = fields.Integer(compute='_compute_step_counts')
-    step_done_count = fields.Integer(compute='_compute_step_counts')
-    step_progress_pct = fields.Float(compute='_compute_step_counts')
+    # step_count + step_done_count are stored (drive list views / stat
+    # buttons in Task 1.8). step_progress_pct stays non-stored — it's a
+    # cheap derivative. Odoo flags as inconsistent when stored and
+    # non-stored fields share a compute method, so they get distinct
+    # methods below.
+    step_count = fields.Integer(compute='_compute_step_counts', store=True)
+    step_done_count = fields.Integer(compute='_compute_step_counts', store=True)
+    step_progress_pct = fields.Float(compute='_compute_step_progress_pct')
     current_step_id = fields.Many2one(
         'fp.job.step',
         compute='_compute_current_step',
@@ -199,6 +204,10 @@ class FpJob(models.Model):
         for job in self:
             job.step_count = len(job.step_ids)
             job.step_done_count = len(job.step_ids.filtered(lambda s: s.state == 'done'))
+
+    @api.depends('step_count', 'step_done_count')
+    def _compute_step_progress_pct(self):
+        for job in self:
             job.step_progress_pct = (
                 (job.step_done_count / job.step_count * 100.0)
                 if job.step_count else 0.0

fusion_plating/fusion_plating/models/fp_job_step.py

@@ -76,6 +76,39 @@ class FpJobStep(models.Model):
     duration_actual = fields.Float(string='Actual Minutes', readonly=True)
     instructions = fields.Html(string='Step Instructions')
 
+    # ------------------------------------------------------------------
+    # State machine — actions
+    # ------------------------------------------------------------------
+    # Implemented: button_start (ready/paused → in_progress),
+    #              button_finish (in_progress → done).
+    # Stubs (raise NotImplementedError for Task 1.6):
+    #              button_pause   (in_progress → paused)
+    #              button_resume  (covered by button_start when state='paused')
+    #              button_skip    (pending/ready → skipped)
+    #              button_cancel  (any non-done → cancelled)
+    # Predecessor-driven transition pending → ready will land in
+    # Task 1.6 along with first-step / dependency wiring.
+    # ------------------------------------------------------------------
+
+    def button_pause(self):
+        raise NotImplementedError(_(
+            "button_pause lands in Task 1.6 (operator pause / break / "
+            "end-of-shift). Use button_finish to complete a step or set "
+            "state directly via privileged code."
+        ))
+
+    def button_skip(self):
+        raise NotImplementedError(_(
+            "button_skip lands in Task 1.6 (skip an opt-in step that "
+            "wasn't activated for this job)."
+        ))
+
+    def button_cancel(self):
+        raise NotImplementedError(_(
+            "button_cancel lands in Task 1.6 (cancelling a single step; "
+            "cancelling the whole job runs through fp.job.action_cancel)."
+        ))
+
     def button_start(self):
         for step in self:
             if step.state not in ('ready', 'paused'):
@@ -95,6 +128,11 @@ class FpJobStep(models.Model):
                     "Step '%s' is in state '%s' — only in-progress steps can finish."
                 ) % (step.name, step.state))
             step.state = 'done'
-            step.date_finished = fields.Datetime.now()
-            step.finished_by_user_id = self.env.user
+            # First-finish audit (mirrors button_start's first-start guard).
+            # If a future rework flow re-opens then re-finishes, the original
+            # finish timestamp/user is preserved. duration_actual rollups
+            # in Task 1.7 will use timelog rows for the latest interval.
+            if not step.date_finished:
+                step.date_finished = fields.Datetime.now()
+                step.finished_by_user_id = self.env.user
         return True