feat(observer): heuristic reasoning capture in primary_rationale

Closes brain-retro 2026-05-20 #6 — extractTriggers/Candidates/Boundaries
scan assistant.text for Pravila §N / ADR-N / PSR_v1 RX / routing-off-phase
LN / hard-floor + numbered/bulleted lists (≥2). Populates previously-
always-empty primary_rationale arrays.

Conservative-broad: false positives accepted (mention ≠ application);
/brain-retro determines applied validity. Phase 2 agent-judge out of scope.

19 new tests, 282/282 GREEN.

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

tools/observer-transcript-parser.mjs

@@ -290,6 +290,77 @@ export function extractTokenUsage(turn) {
  * For each AskUserQuestion toolUseResult in the turn, emit one event per question.
  * answer_kind: 'option' (exact label match), 'custom' (free-text), 'no_answer' (missing/empty).
  */
+/** Collect concatenated text from all assistant text blocks in the turn. */
+function assistantTextOfTurn(turn) {
+  const parts = [];
+  for (const e of turn || []) {
+    if (!e || !e.message || e.message.role !== 'assistant') continue;
+    const content = Array.isArray(e.message.content) ? e.message.content : [];
+    for (const b of content) {
+      if (b && b.type === 'text' && typeof b.text === 'string') parts.push(b.text);
+    }
+  }
+  return parts.join('\n');
+}
+
+const TRIGGER_PATTERNS = [
+  /\bPravila\s+§\d+(?:\.\d+)?/g,
+  /\bADR-\d+/g,
+  /\bPSR_v1\s+R\d+(?:\.\d+)?/g,
+  /\brouting-off-phase\s+L\d+/g,
+  /\bL\d+\s+chain/g,
+  /\bhard-(?:floor|rule)\b/gi,
+];
+
+/** Heuristic triggers from assistant text. Conservative-broad — false positives OK. */
+export function extractTriggers(turn) {
+  const text = assistantTextOfTurn(turn);
+  const out = new Set();
+  for (const re of TRIGGER_PATTERNS) {
+    const matches = text.match(re);
+    if (matches) for (const m of matches) {
+      const norm = /^L\d+\s+chain$/.test(m) ? `routing-off-phase ${m.split(/\s+/)[0]}` : m;
+      out.add(norm);
+    }
+  }
+  return [...out];
+}
+
+const CANDIDATE_NUMBERED_RE = /^\s*\d+[.\)]\s+([^\n]+)$/gm;
+const CANDIDATE_BULLET_RE = /^\s*[-*]\s+([^\n]+)$/gm;
+
+/** Heuristic candidates: ≥2 numbered (preferred) or bulleted items. */
+export function extractCandidates(turn) {
+  const text = assistantTextOfTurn(turn);
+  const numbered = [...text.matchAll(CANDIDATE_NUMBERED_RE)].map((m) => m[1].trim());
+  if (numbered.length >= 2) return numbered;
+  const bulleted = [...text.matchAll(CANDIDATE_BULLET_RE)].map((m) => m[1].trim());
+  if (bulleted.length >= 2) return bulleted;
+  return [];
+}
+
+const BOUNDARY_PATTERNS = [
+  /\bADR-\d+(?:\s+§\d+(?:\.\d+)?)?/g,
+  /\bPSR_v1\s+R\d+(?:\.\d+)?/g,
+  /\bPravila\s+§\d+(?:\.\d+)?/g,
+  /\brouting-off-phase\s+L\d+/g,
+  /\bL\d+\s+chain/g,
+];
+
+/** Heuristic boundaries — overlaps with triggers, dedup per-array only. */
+export function extractBoundaries(turn) {
+  const text = assistantTextOfTurn(turn);
+  const out = new Set();
+  for (const re of BOUNDARY_PATTERNS) {
+    const matches = text.match(re);
+    if (matches) for (const m of matches) {
+      const norm = /^L\d+\s+chain$/.test(m) ? `routing-off-phase ${m.split(/\s+/)[0]}` : m;
+      out.add(norm);
+    }
+  }
+  return [...out];
+}
+
 export function extractAskUserQuestionEvents(turn) {
   const events = [];
   for (const e of turn || []) {
@@ -528,9 +599,9 @@ export function parseTranscript(transcriptText, fallbackSessionId = null) {
     primary_rationale: {
       step: 1,
       node_chosen: skills.length > 0 ? skills[0] : 'direct',
-      triggers_matched: [],
-      candidates_considered: [],
-      boundaries_applied: [],
+      triggers_matched: extractTriggers(turn),
+      candidates_considered: extractCandidates(turn),
+      boundaries_applied: extractBoundaries(turn),
       hard_floor: usedSuperpowers
         ? { invoked: true, rules: ['Pravila §12'] }
         : { invoked: false, rules: [] },