feat(tools): add letter length + summary depth controls; harden korrespond §-discipline

- Summarize: new depth param (brief/standard/detailed) with depth-aware prompt
  instructions and coverage mandate; wired through API + JS
- Korrespond: new letter length param (concise/standard/detailed) injected as
  Lengde: instruction in draft pass; wired through API + JS
- Korrespond draft prompt: add §-discipline rule (cite only directly relevant §§)
  plus Opphevet guard (aligned with dobetterlegal-tools)

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

includes/LegalTools.php

@@ -1854,7 +1854,8 @@ PROMPT;
         string $text,
         string $language = 'en',
         string $engine = 'azure_mini',
-        string $corpusContext = ''
+        string $corpusContext = '',
+        string $depth = 'standard'
     ): array {
         $text   = $this->requirePasteText($text);
         $engine = in_array($engine, ['azure_mini', 'azure_full', 'gpu'], true) ? $engine : 'azure_mini';
@@ -1870,16 +1871,34 @@ PROMPT;
                 . $text;
         }
 
+        $depthInstructions = match($depth) {
+            'brief'    => [
+                'what_we_found' => '1-2 sentence executive summary covering the main outcome',
+                'key_facts'     => 'up to 3 most important facts',
+                'coverage'      => '',
+            ],
+            'detailed' => [
+                'what_we_found' => 'comprehensive 6-10 sentence summary covering every fact, decision, party, date, and legal implication',
+                'key_facts'     => 'every fact, decision, and legal reference mentioned in the document',
+                'coverage'      => "\nCover ALL parties, ALL key decisions, ALL dates, and ALL legal references present in the document. Do not omit facts because they seem minor — err on the side of inclusion.",
+            ],
+            default    => [
+                'what_we_found' => '3-5 sentence summary covering all key outcomes, parties, and decisions',
+                'key_facts'     => 'all key facts',
+                'coverage'      => "\nCover ALL parties, ALL key decisions, ALL dates, and ALL legal references present in the document.",
+            ],
+        };
+
         $prompt = <<<PROMPT
 Summarise the following document in {$locale}. Do not invent facts not present in the text.
-Return JSON only — no extra text before or after the JSON object.
+Return JSON only — no extra text before or after the JSON object.{$depthInstructions['coverage']}
 
 {$enriched}
 
 Return this JSON structure:
 {
-  "what_we_found": "plain-language summary (2-4 sentences)",
-  "key_facts": ["fact 1", "fact 2"],
+  "what_we_found": "{$depthInstructions['what_we_found']}",
+  "key_facts": ["{$depthInstructions['key_facts']}"],
   "dates": ["date or event phrase"],
   "parties": ["party or role"],
   "legal_references_detected": ["statute, article, or case name"],