refactor(frontend): the last pay-down, part 1 — three dead views deleted, editor rules shared, .page-container + .fs-input canon, rules-shared.css; a one-declaration CSS body is not a shape (#2903, milestone 299 step 5)

The derive queue said the biggest duplicate families were whole views:
TaskViewerView, UserManagementView and LogsView were imported nowhere — left
behind when tasks moved to the editor and users/logs became SettingsView
tabs. Deleted (rule 22). Note/TaskEditorView carried six identical scoped
rules -> editor-shared.css (the .tag-suggest-row gap the scoped copies
actually rendered wins). Three views wrapped the page under three names ->
.page-container in components.css. Three scoped input recipes -> the design
system fs-input recipe (snippet #2336), verbatim, in components.css; width/
box-sizing stay with the caller. The three rules panes share .pane and the
pane heading via rules-shared.css (the auth-shared pattern, #2852).

Ledger: a single-declaration CSS rule keeps its selector in its fingerprint,
so `color: var(--fs-text-tertiary)` under five different names is no longer
a five-file "identical body" family — the first pay-down found that most of
the 148 dup families were exactly this, and nobody would consolidate them.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/scribe/services/coverage.py

@@ -156,6 +156,12 @@ def _block_sha(lines: list[str]) -> str:
     return hashlib.sha1("\n".join(kept).encode("utf-8")).hexdigest()[:16]
 
 
+def _declaration_count(lines: list[str]) -> int:
+    """How many `prop: value` declarations a CSS block body carries."""
+    body = " ".join(lines)
+    return sum(1 for part in body.replace("}", "").split(";") if ":" in part)
+
+
 def extract_definitions(text: str) -> list[Definition]:
     """Every definition this text makes, with signature + fingerprint.
 
@@ -202,6 +208,15 @@ def extract_definitions(text: str) -> list[Definition]:
             hashed = head + block[1:]
             if not any(x.strip() for x in hashed):
                 hashed = block
+            # A SINGLE declaration is not a shape (#2903): `color: var(--fs-
+            # text-tertiary)` under .text-muted, .task-mark and .pin-badge-auto
+            # is three meanings sharing one line, not three copies of one
+            # rule — the first pay-down found 5-file "families" of exactly
+            # this and nobody would consolidate them. Keep the selector in the
+            # hash for one-liners, so they group only with same-name copies;
+            # two declarations and up stay selector-agnostic.
+            elif _declaration_count(hashed) < 2:
+                hashed = block
         else:
             hashed = block
         out.append(Definition(