feat(fusion_plating_jobs): fp.job.step blocker_kind/reason/jump_target computes

Plan task P1.2. Reuses _fp_should_block_predecessors so the new compute
stays in sync with the existing can_start logic. Drives the OWL GateViz
component on the tablet — "Can't start yet — Waiting on Step N: X".

Future work: extend with explicit branches for contract_review /
parts_not_received / racking_required / manager_input as those gate
models mature.

Tests not run locally (no fusion_plating mount in odoo-modsdev).
Verify on entech: -u fusion_plating_jobs --test-tags fp_jobs.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

fusion_plating/fusion_plating_jobs/models/fp_job_step.py

@@ -85,6 +85,72 @@ class FpJobStep(models.Model):
             )
             step.can_start = not bool(blocking)
 
+    # Gate visualizer — drives the OWL GateViz component on the tablet.
+    # Returns kind of blocker + human reason + optional (model, id) jump
+    # target. Reuses _fp_should_block_predecessors so this stays in sync
+    # with can_start as a single source of truth.
+    blocker_kind = fields.Selection(
+        [
+            ('none',                 'Not blocked'),
+            ('predecessor',          'Waiting on predecessor'),
+            ('contract_review',      'Contract review pending'),
+            ('parts_not_received',   'Parts not received'),
+            ('racking_required',     'Racking inspection required'),
+            ('manager_input',        'Manager input required'),
+            ('other',                'Other'),
+        ],
+        compute='_compute_blocker',
+        string='Blocker Kind',
+    )
+    blocker_reason = fields.Char(
+        compute='_compute_blocker',
+        string='Blocker Reason',
+        help='Human-readable explanation surfaced in the GateViz block.',
+    )
+    blocker_jump_target_model = fields.Char(compute='_compute_blocker')
+    blocker_jump_target_id = fields.Integer(compute='_compute_blocker')
+
+    @api.depends(
+        'state', 'sequence', 'parallel_start', 'requires_predecessor_done',
+        'job_id.enforce_sequential',
+        'job_id.step_ids.state', 'job_id.step_ids.sequence',
+    )
+    def _compute_blocker(self):
+        for step in self:
+            # Terminal/in-progress states are never "blocked"
+            if step.state in ('done', 'skipped', 'cancelled', 'in_progress'):
+                step.blocker_kind = 'none'
+                step.blocker_reason = ''
+                step.blocker_jump_target_model = False
+                step.blocker_jump_target_id = 0
+                continue
+
+            # Predecessor gate — same policy as _compute_can_start
+            if step._fp_should_block_predecessors():
+                earlier_open = step.job_id.step_ids.filtered(lambda x: (
+                    x.id != step.id
+                    and x.sequence < step.sequence
+                    and x.state not in ('done', 'skipped', 'cancelled')
+                ))
+                if earlier_open:
+                    first_blocker = earlier_open.sorted('sequence')[0]
+                    step.blocker_kind = 'predecessor'
+                    seq_disp = (first_blocker.sequence or 0) // 10
+                    step.blocker_reason = (
+                        f'Waiting on Step {seq_disp}: {first_blocker.name}'
+                    )
+                    step.blocker_jump_target_model = 'fp.job.step'
+                    step.blocker_jump_target_id = first_blocker.id
+                    continue
+
+            # Future: extend with explicit checks for contract_review /
+            # parts_not_received / racking_required / manager_input as
+            # those gate models mature. For now, default to 'none'.
+            step.blocker_kind = 'none'
+            step.blocker_reason = ''
+            step.blocker_jump_target_model = False
+            step.blocker_jump_target_id = 0
+
     # NOTE: the actual button_start override lives further down (~line
     # 876) where it merges Sub 13 predecessor gate + Policy B Contract
     # Review auto-open + Sub 8 Racking auto-open + the receiving soft