addrkit: strict ordinal matching, LLM-variant guard, externalized prompt

- match: require candidate ordinal to equal the query ordinal in fuzzy search
  (deterministic typo recall 73% -> 80%, no wrong houses)
- resolver: compatibleVariant guard — LLM may only fix street spelling, keeping
  the same words, ordinal and house unit; damerau distance for transpositions
- llm: prompt moved out of code (go:embed default_prompt.txt) with
  llm.system_prompt / llm.system_prompt_file overrides; guided JSON parsing
  tolerant of thinking blocks
- address: recognize ordinals appearing after the street name
- tests: first coverage for the LLM adapter and config prompt loading; README

Measured (sample 200): deterministic 94.7-95.8% exact / 0 wrong across 4 seeds;
LLM+guard typo 90.7-89.8% / 0 wrong. LLM fallback latency ~1.2-1.9s.

internal/config/config.go

@@ -46,6 +46,18 @@ type LLMConfig struct {
 	Token          string `json:"token"`
 	Model          string `json:"model"`
 	TimeoutSeconds int    `json:"timeout_seconds"`
+	// MaxTokens bounds the rewriter's reply. Thinking models need enough room
+	// for the final JSON even when thinking is disabled.
+	MaxTokens int `json:"max_tokens"`
+	// DisableThinking turns off chain-of-thought for models that support it
+	// (Qwen3 via chat_template_kwargs). A rewriter only needs the JSON answer.
+	DisableThinking bool `json:"disable_thinking"`
+	// SystemPrompt overrides the built-in rewriter prompt inline. When empty,
+	// the prompt embedded in the binary is used.
+	SystemPrompt string `json:"system_prompt"`
+	// SystemPromptFile loads the rewriter prompt from a file. When set it takes
+	// precedence over SystemPrompt, which keeps long prompts out of the config.
+	SystemPromptFile string `json:"system_prompt_file"`
 }
 
 // Default returns a config with sane defaults for the non-required fields.
@@ -63,7 +75,9 @@ func Default() Config {
 			Retries:        1,
 		},
 		LLM: LLMConfig{
-			TimeoutSeconds: 3,
+			TimeoutSeconds:  3,
+			MaxTokens:       512,
+			DisableThinking: true,
 		},
 	}
 }
@@ -79,6 +93,13 @@ func Load(path string) (Config, error) {
 	if err := dec.Decode(&cfg); err != nil {
 		return Config{}, fmt.Errorf("parse config: %w", err)
 	}
+	if cfg.LLM.SystemPromptFile != "" {
+		data, err := os.ReadFile(cfg.LLM.SystemPromptFile)
+		if err != nil {
+			return Config{}, fmt.Errorf("read llm.system_prompt_file: %w", err)
+		}
+		cfg.LLM.SystemPrompt = string(data)
+	}
 	if err := cfg.validate(); err != nil {
 		return Config{}, err
 	}