Clean up stale comments, dead code, and code quality issues

- Remove dead code: unused PENDING_FILE, _extract_domain(), sender_domain
  field, imap_uid fallback, check_unseen_only config key
- Fix stale comments: removed tag references in README and docstrings,
  top_domains -> top_senders, 1-based number -> scan_index number
- Make _extract_email_address public (used by 3 modules)
- Extract _format_address helper to deduplicate from/to parsing
- Batch pending queue disk I/O in review act/accept (load once, save once)
- Reuse cleared pending dict in scan instead of redundant disk load
- Track envelope IDs during scan loop to catch duplicates
- Fix default confidence_threshold 75 -> 85 to match config and docs
- Update get_relevant_examples default n=10 -> n=5 to match caller
- Add graceful error for --recent with non-numeric value

scripts/email_processor/classifier.py

@@ -47,8 +47,8 @@ def _build_prompt(email_data, config):
     max_body = config.get("rules", {}).get("max_body_length", 1000)
 
     # Gather learning context from decision history
-    examples = decision_store.get_relevant_examples(email_data, n=10)
-    sender_email = decision_store._extract_email_address(email_data.get("sender", ""))
+    examples = decision_store.get_relevant_examples(email_data, n=5)
+    sender_email = decision_store.extract_email_address(email_data.get("sender", ""))
     sender_stats = decision_store.get_sender_stats(sender_email) if sender_email else {}
     known_labels = decision_store.get_known_labels()
 
@@ -80,7 +80,7 @@ def _build_prompt(email_data, config):
     # Section 4: Few-shot examples (top 5 most relevant past decisions)
     if examples:
         parts.append("\n--- Past decisions (learn from these) ---")
-        for ex in examples[:5]:
+        for ex in examples:
             parts.append(
                 f"From: {ex['sender'][:60]} | To: {ex['recipient'][:40]} | "
                 f"Subject: {ex['subject'][:60]} -> {ex['action']}"
@@ -135,9 +135,9 @@ def _parse_response(output):
 
     Expected format (one per line):
         Action: delete
-        Tags: promotion, marketing, newsletter
+        Tags: promotion, newsletter, social
         Summary: Promotional offer from retailer
-        Reason: Clearly a marketing email with discount offer
+        Reason: Clearly a promotional email with discount offer
 
     Falls back to safe defaults (keep, empty tags) on parse failure.
     """