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/decision_store.py

@@ -25,7 +25,6 @@ from collections import Counter
 SCRIPT_DIR = Path(__file__).parent
 DATA_DIR = SCRIPT_DIR / "data"
 HISTORY_FILE = DATA_DIR / "decision_history.json"
-PENDING_FILE = DATA_DIR / "pending_emails.json"
 
 # Stop-words excluded from subject keyword matching to reduce noise.
 _STOP_WORDS = {"re", "fwd", "the", "a", "an", "is", "to", "for", "and", "or", "your", "you"}
@@ -50,18 +49,7 @@ def _save_history(history):
         json.dump(history, f, indent=2, ensure_ascii=False)
 
 
-def _extract_domain(sender):
-    """Extract the domain part from a sender string.
-
-    Handles formats like:
-        "Display Name <user@example.com>"
-        user@example.com
-    """
-    match = re.search(r"[\w.+-]+@([\w.-]+)", sender)
-    return match.group(1).lower() if match else ""
-
-
-def _extract_email_address(sender):
+def extract_email_address(sender):
     """Extract the full email address from a sender string."""
     match = re.search(r"([\w.+-]+@[\w.-]+)", sender)
     return match.group(1).lower() if match else sender.lower()
@@ -85,7 +73,6 @@ def record_decision(email_data, action, source="user", tags=None):
     entry = {
         "timestamp": datetime.now().isoformat(timespec="seconds"),
         "sender": email_data.get("sender", ""),
-        "sender_domain": _extract_domain(email_data.get("sender", "")),
         "recipient": email_data.get("recipient", ""),
         "subject": email_data.get("subject", ""),
         "summary": email_data.get("summary", ""),
@@ -98,7 +85,7 @@ def record_decision(email_data, action, source="user", tags=None):
     return entry
 
 
-def get_relevant_examples(email_data, n=10):
+def get_relevant_examples(email_data, n=5):
     """Find the N most relevant past decisions for a given email.
 
     Relevance is scored by two signals:
@@ -112,7 +99,7 @@ def get_relevant_examples(email_data, n=10):
     if not history:
         return []
 
-    target_email = _extract_email_address(email_data.get("sender", ""))
+    target_email = extract_email_address(email_data.get("sender", ""))
     target_words = (
         set(re.findall(r"\w+", email_data.get("subject", "").lower())) - _STOP_WORDS
     )
@@ -122,7 +109,7 @@ def get_relevant_examples(email_data, n=10):
         score = 0
 
         # Signal 1: sender email match
-        if target_email and _extract_email_address(entry.get("sender", "")) == target_email:
+        if target_email and extract_email_address(entry.get("sender", "")) == target_email:
             score += 3
 
         # Signal 2: subject keyword overlap
@@ -146,7 +133,7 @@ def get_sender_stats(sender_email):
     history = _load_history()
     actions = Counter()
     for entry in history:
-        if _extract_email_address(entry.get("sender", "")) == sender_email:
+        if extract_email_address(entry.get("sender", "")) == sender_email:
             actions[entry["action"]] += 1
     return dict(actions)
 
@@ -171,7 +158,7 @@ def compute_confidence(sender_email, action, tags):
     # Find past decisions with same sender and sufficient tag overlap
     matches = []
     for entry in history:
-        entry_email = _extract_email_address(entry.get("sender", ""))
+        entry_email = extract_email_address(entry.get("sender", ""))
         if entry_email != sender_email:
             continue
 
@@ -216,7 +203,7 @@ def get_known_labels():
 def get_all_stats():
     """Compute aggregate statistics across the full decision history.
 
-    Returns a dict with keys: total, by_action, by_source, top_domains.
+    Returns a dict with keys: total, by_action, by_source, top_senders.
     Returns None if history is empty.
     """
     history = _load_history()
@@ -228,7 +215,7 @@ def get_all_stats():
     by_source = Counter(e["source"] for e in history)
 
     # Top 10 sender addresses by decision count
-    sender_counts = Counter(_extract_email_address(e.get("sender", "")) for e in history)
+    sender_counts = Counter(extract_email_address(e.get("sender", "")) for e in history)
     top_senders = sender_counts.most_common(10)
 
     return {