refactor: phase 3 - API efficiency improvements

Add typed dataclasses for tuple returns:
- types.py: HeadlineItem, FetchResult, Block dataclasses with legacy tuple converters
- fetch.py: Add type hints and HeadlineTuple type alias

Add pyright for static type checking:
- Add pyright to dependencies
- Verify type coverage with pyright (0 errors in core modules)

This enables:
- Named types instead of raw tuples (better IDE support, self-documenting)
- Type-safe APIs across modules
- Backward compatibility via to_tuple/from_tuple methods

Note: Lazy imports skipped for render.py - startup impact is minimal.

engine/fetch.py

@@ -8,6 +8,7 @@ import pathlib
 import re
 import urllib.request
 from datetime import datetime
+from typing import Any
 
 import feedparser
 
@@ -16,9 +17,13 @@ from engine.filter import skip, strip_tags
 from engine.sources import FEEDS, POETRY_SOURCES
 from engine.terminal import boot_ln
 
+# Type alias for headline items
+HeadlineTuple = tuple[str, str, str]
+
 
 # ─── SINGLE FEED ──────────────────────────────────────────
-def fetch_feed(url):
+def fetch_feed(url: str) -> Any | None:
+    """Fetch and parse a single RSS feed URL."""
     try:
         req = urllib.request.Request(url, headers={"User-Agent": "mainline/0.1"})
         resp = urllib.request.urlopen(req, timeout=config.FEED_TIMEOUT)
@@ -28,8 +33,9 @@ def fetch_feed(url):
 
 
 # ─── ALL RSS FEEDS ────────────────────────────────────────
-def fetch_all():
-    items = []
+def fetch_all() -> tuple[list[HeadlineTuple], int, int]:
+    """Fetch all RSS feeds and return items, linked count, failed count."""
+    items: list[HeadlineTuple] = []
     linked = failed = 0
     for src, url in FEEDS.items():
         feed = fetch_feed(url)
@@ -59,7 +65,7 @@ def fetch_all():
 
 
 # ─── PROJECT GUTENBERG ────────────────────────────────────
-def _fetch_gutenberg(url, label):
+def _fetch_gutenberg(url: str, label: str) -> list[HeadlineTuple]:
     """Download and parse stanzas/passages from a Project Gutenberg text."""
     try:
         req = urllib.request.Request(url, headers={"User-Agent": "mainline/0.1"})