Fix Feature 12 review findings F2–F8 on Regular grounding and onboarding

Grounding (F2–F5):
- Each ground_dinner job carries the dinner's new grounding_revision
  (migration 0010). Renaming a pending Regular raises the revision, and a
  job only grounds and writes a dinner still at its revision, so a queued
  original job no longer grounds the new name or decides the outcome.
- Background grounding keeps a method, minutes or difficulty a member saved
  while the Regular was pending, and fills only those left empty.
- Grounding by hand clears the pasted recipe_url, and link deduplication
  uses the source_url of the attached recipe, else the pending link.
- Archived dinners are not grounded: the job checks before any search,
  fetch or model call, and its final update requires an unarchived row.

Onboarding (F6, F7):
- Step 3 shows "Add Regulars" back to step 2 when the server refuses to
  finish with fewer than three Regulars.
- Common picks are hidden by a copy of harness Normalize/Similar, checked
  against the same shared cases as the Go code.

Docs (F8): ARCHITECTURE.md covers the three-Regular minimum, step-3
recovery, the grounding revision and the dedupe rules.

F1 was fixed in 1304487; its test now also asserts the old link is never
grounded and recipe_url stays cleared.

Maestro task 5037ff86-181d-448e-927b-c2fd2258a25d.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/ai/harness/dedupe_test.go

@@ -1,10 +1,45 @@
 package harness
 
 import (
+	"encoding/json"
+	"os"
 	"testing"
 	"unicode"
 )
 
+// TestSharedDedupeCases runs testdata/dedupe_cases.json, which the PWA's
+// copy of Normalize and Similar (web/src/dinners/names.ts) runs too, so the
+// two cannot drift apart on these names.
+func TestSharedDedupeCases(t *testing.T) {
+	raw, err := os.ReadFile("testdata/dedupe_cases.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	var cases struct {
+		Normalize []struct{ Name, Want string }
+		Similar   []struct {
+			A, B string
+			Want bool
+		}
+	}
+	if err := json.Unmarshal(raw, &cases); err != nil {
+		t.Fatal(err)
+	}
+	if len(cases.Normalize) == 0 || len(cases.Similar) == 0 {
+		t.Fatal("dedupe_cases.json has no cases")
+	}
+	for _, c := range cases.Normalize {
+		if got := Normalize(c.Name); got != c.Want {
+			t.Errorf("Normalize(%q) = %q, want %q", c.Name, got, c.Want)
+		}
+	}
+	for _, c := range cases.Similar {
+		if got := Similar(c.A, c.B); got != c.Want {
+			t.Errorf("Similar(%q, %q) = %v, want %v", c.A, c.B, got, c.Want)
+		}
+	}
+}
+
 func TestNormalize(t *testing.T) {
 	tests := []struct {
 		name, want string