fix: fix: architect should resume session when processing answers on an accepted sprint PR (#436)

When the architect processes human answers to design questions (answer_parsing step),
it now resumes the session from the research/questions run instead of starting fresh.
This preserves Claude's deep codebase understanding from the research phase, ensuring
sub-issues include specific file references and implementation details.

Changes:
- architect-run.sh: Added detect_questions_phase() to check if PR is in questions phase
  (has `## Design forks` section and question comments). If so, resume the session
  from SID_FILE to preserve context.
- formulas/run-architect.toml: Documented session resumption behavior in answer_parsing step.

Session is only preserved when PR is in questions-awaiting-answers phase. Fresh sessions
are started for new pitches (no stale context from old sprints).

formulas/run-architect.toml

@@ -244,6 +244,17 @@ title = "Answer parsing + sub-issue filing (issue #102)"
 description = """
 This step processes human answers to design questions and files sub-issues.
 
+## Session resumption
+
+When processing answers, the architect resumes the session from the research/questions
+run (step 2) to preserve codebase context. This ensures Claude has full understanding
+of dispatcher.sh, vault.sh, branch-protection.sh, and all formulas when filing
+sub-issues, resulting in more specific file references and implementation details.
+
+The session ID is persisted to `$SID_FILE` after the research/questions run. On
+answer_parsing runs, if the PR is in the questions phase, the session is resumed
+instead of starting fresh.
+
 ## Preflight: Detect PRs in question phase
 
 An architect PR is in the question phase if ALL of the following are true: