Narration: kill label-parroting at the source + reduce gate false positives

Traces showed two remaining issues: the model parroted 'park garden'/'place of
worship' from the 'Weights extracted:' prompt line (removed it + dropped the now
dead _weights_summary), and the gate kept rejecting lone sentence-starters
('Stepping'). Add a comprehensive common-word set instead of a blanket single-word
pass (which had let the planted 'Eiffel Tower' through). Guarantee intact: all
multi-word invented venues still caught.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/discoverroute/narrate/grounding.py

@@ -38,8 +38,20 @@ _COMMON = {
     "just", "main", "canvas", "serene", "golden", "thread", "serendipity",
     "awaits", "loop", "tucked", "secret", "alcove", "heart", "memory", "story",
     "stories", "forgotten", "damp", "concrete", "dusty", "afternoon", "sky",
-    "subway", "grid", "skyscrapers", "skyscraper", "serenity", "canvas", "echoes",
+    "subway", "grid", "skyscrapers", "skyscraper", "serenity", "echoes",
     "whisper", "whispers", "glow", "shimmer", "quietude",
+    # common sentence-starting verbs/adverbs the model opens clauses with — never
+    # venues, but capitalized at a sentence boundary the extractor would flag them.
+    "stepping", "step", "begin", "beginning", "enter", "entering", "exit",
+    "leave", "leaving", "approach", "approaching", "imagine", "imagining",
+    "picture", "notice", "noticing", "feel", "feeling", "soon", "duck", "ducking",
+    "glance", "linger", "lingering", "explore", "exploring", "discover",
+    "discovering", "meander", "meandering", "amble", "ambling", "saunter",
+    "sauntering", "carry", "carrying", "move", "moving", "emerge", "emerging",
+    "drift", "drifting", "ahead", "beyond", "below", "above", "around", "alongside",
+    "tucked", "nestled", "perched", "wrapped", "framed", "lit", "bathed",
+    "morning", "midday", "twilight", "moment", "moments", "pause", "rest",
+    "finally", "eventually", "meanwhile", "soon", "shortly", "nearby", "opposite",
     # template/narration sentence-starters and connective words
     "why", "spending", "every", "threads", "discoveries", "real", "spot",
     "nothing", "invented", "breath", "hush", "shelves", "stalls", "something",

src/discoverroute/narrate/narrate.py

@@ -230,15 +230,6 @@ def narrate(plain, discovery, pois, vibe="", mode="walk", start_label="",
     return template, False  # fail-closed: ship the grounded template
 
 
-def _weights_summary(weights) -> str:
-    """Compact 'cafe 0.9, park 0.7' line from the extracted weights, if any."""
-    aff = getattr(weights, "category_affinity", None)
-    if not aff:
-        return ""
-    top = sorted(aff, key=aff.get, reverse=True)[:5]
-    return ", ".join(f"{c.replace('_', ' ')} {aff[c]:.2f}" for c in top)
-
-
 def _llm_narration(plain, discovery, pois, vibe, mode, start_label, end_label,
                    weights=None, geo_allowed=None, city_label="") -> str:
     """Generate narration with MiniCPM5-1B, constrained to the allowed names.
@@ -257,7 +248,6 @@ def _llm_narration(plain, discovery, pois, vibe, mode, start_label, end_label,
     bullet = "\n".join(f"- {n}" for n in names)
     extra = round(discovery.time_min - plain.time_min)
     total_min = round(discovery.time_min + getattr(discovery, "dwell_s", 0.0) / 60.0)
-    weights_line = _weights_summary(weights)
     guide = f"{city_label} " if city_label else ""
     context_terms = ", ".join(geo_allowed) if geo_allowed else ""
 
@@ -284,7 +274,6 @@ def _llm_narration(plain, discovery, pois, vibe, mode, start_label, end_label,
     )
     user = (
         f"Vibe: {vibe or 'open to anything'}\n"
-        + (f"Weights extracted: {weights_line}\n" if weights_line else "")
         + f"Mode: {mode} from {start_label or 'the start'} to "
         f"{end_label or 'the destination'}\n"
         + (f"You may reference (scene-setting, name freely): {context_terms}\n"