Display metric units in web UI, make seed idempotent, simplify code

- Load m.unit in get_domain() so MetricBound carries units from DB
- Add Unit column to domains list template
- Make load_transport_seed() idempotent with IntegrityError handling
  and metric unit backfill for existing DBs
- Remove unused imports (json, sqlite3, Entity)
- Simplify combinator loop to list comprehension
- Merge duplicate conditional/valid branches in pipeline
- Consolidate duplicated SQL in get_all_results()
- Expand CLAUDE.md with fuller architecture docs and conventions

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/physcom/engine/pipeline.py

@@ -157,14 +157,13 @@ class Pipeline:
                         result.pass1_blocked += 1
                         self._update_run_counters(run_id, result, current_pass=1)
                         continue  # blocked — skip remaining passes
-                    elif cr.status == "conditional":
-                        combo.status = "valid"
-                        self.repo.update_combination_status(combo.id, "valid")
-                        result.pass1_conditional += 1
                     else:
                         combo.status = "valid"
                         self.repo.update_combination_status(combo.id, "valid")
-                        result.pass1_valid += 1
+                        if cr.status == "conditional":
+                            result.pass1_conditional += 1
+                        else:
+                            result.pass1_valid += 1
 
                     self._update_run_counters(run_id, result, current_pass=1)
                 elif 1 in passes: