feat(truthsocial): Add Truth Social as opt-in source

Mastodon-compatible API at truthsocial.com/api/v2/search.
Opt-in via TRUTHSOCIAL_TOKEN env var (bearer token from browser).
Silent when unconfigured. Full pipeline: search, parse, normalize,
score, dedupe, render across all 10 pipeline files.

27 new tests, 440 total passing.

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

scripts/lib/env.py

@@ -257,6 +257,7 @@ def get_config() -> Dict[str, Any]:
         ('CT0', None),
         ('BSKY_HANDLE', None),
         ('BSKY_APP_PASSWORD', None),
+        ('TRUTHSOCIAL_TOKEN', None),
     ]
 
     for key, default in keys:
@@ -490,6 +491,14 @@ def is_bluesky_available(config: Dict[str, Any]) -> bool:
     return bool(config.get('BSKY_HANDLE') and config.get('BSKY_APP_PASSWORD'))
 
 
+def is_truthsocial_available(config: Dict[str, Any]) -> bool:
+    """Check if Truth Social source is available.
+
+    Requires TRUTHSOCIAL_TOKEN (bearer token from browser dev tools).
+    """
+    return bool(config.get('TRUTHSOCIAL_TOKEN'))
+
+
 def is_polymarket_available() -> bool:
     """Check if Polymarket source is available.