addrkit: quality evaluation harness + parser hardening

- add internal/eval: deterministic citizen-style perturbation harness
  (typos, case, word order, abbreviations, filler words, dropped units)
- parser: strip all street-type tokens, filler words (город/дом/д/область),
  trailing apartment (кв N); handle letter-before-fraction and corpus letters
- matching: token-aware typo-tolerant street similarity; wider ambiguity
  margin to surface near-collisions instead of guessing
- seed: correct parse-rate accounting, structure-aware de-duplication
- CLI: 'addrkit eval' command; README with measured results

Measured on the real 73,936-row registry: 99.98% parsed, 0 wrong-house
safety violations across 34k+ perturbed cases.

internal/domain/match/index.go

@@ -45,10 +45,15 @@ type Options struct {
 }
 
 // DefaultOptions returns conservative defaults.
+//
+// The ambiguity margin is deliberately generous relative to the token scores:
+// a one-edit match scores 0.95 and a two-edit match 0.90, so a 0.06 margin
+// makes near-collisions (e.g. "Елоховская" vs "Волховская") ambiguous rather
+// than silently picking the closer-but-wrong street.
 func DefaultOptions() Options {
 	return Options{
 		FuzzyThreshold:  0.82,
-		AmbiguityMargin: 0.03,
+		AmbiguityMargin: 0.06,
 		MaxCandidates:   5,
 	}
 }
@@ -182,7 +187,7 @@ func (ix *Index) fuzzyStreets(p address.ParsedAddress) (entries []address.Entry,
 		if p.Ordinal != "" && s.ordinal != "" && p.Ordinal != s.ordinal {
 			continue
 		}
-		if sim := ratio(p.NameKey, s.nameKey); sim > best {
+		if sim := nameSimilarity(p.NameKey, s.nameKey); sim > best {
 			best = sim
 			bestKey = s.key
 		}
@@ -195,7 +200,7 @@ func (ix *Index) fuzzyStreets(p address.ParsedAddress) (entries []address.Entry,
 		if p.Ordinal != "" && s.ordinal != "" && p.Ordinal != s.ordinal {
 			continue
 		}
-		if ratio(p.NameKey, s.nameKey) >= best-ix.opts.AmbiguityMargin {
+		if nameSimilarity(p.NameKey, s.nameKey) >= best-ix.opts.AmbiguityMargin {
 			ambiguousKeys = append(ambiguousKeys, s.key)
 		}
 	}