chore(design-systems): stop teaching one install's kit in product copy

The operator's check: this must be a system for managing design systems, not one
with the FabledSword family built into it.

No LOGIC was coupled — the audit found zero behavioural dependencies. But every
docstring example, every UI placeholder and several comments named this install's
palette, so a stranger creating their first design system was shown
"FabledSword" as the expected shape and `--fs-obsidian` as the expected token.
Examples teach, and these taught the wrong thing.

Placeholders now describe the SHAPE ("Your house style", "--surface-page")
rather than naming one instance's contents, and the token-name placeholder now
says the thing worth saying: name it for its purpose, because `--obsidian` and
`--button-bg` both stop being true the moment the value or the element changes.

Not fixed here, and it is the one real coupling left: DesignView.vue hardcodes
rule 65's button variants and rule 60's type scale as literal arrays, so a
stranger's Design page would display this family's specs. Those arrays exist
because there was no design system to read from — which there now is. They go
when the panel is repointed (#2295), not before.

Scribe's own stylesheet comments ("Moss action-primary per Hybrid") are left
alone: that is the app CONSUMING the family style, which is what dogfooding
looks like, not the tool assuming it.

src/scribe/services/design_stylesheet.py

@@ -18,8 +18,8 @@ has recall, locations, drift checks and merge.
 
 So the division is: this sheet says what the values MEAN; snippets say what
 things LOOK LIKE, in terms of those values. A token named after an element
-(`--fs-button-bg`) is the smell that the two have been mixed — it multiplies
-with every new element, where a purpose name (`--fs-action-primary`) is reused.
+(`--button-bg`) is the smell that the two have been mixed — it multiplies
+with every new element, where a purpose name (`--action-primary`) is reused.
 
 SAFETY
 ------
@@ -203,7 +203,8 @@ def duplicate_values(tokens: Sequence) -> dict[str, list[str]]:
     Two names for one value are either a deliberate alias or the same idea
     recorded twice — the token-level form of the duplicated-definition shape.
     Reported rather than refused: a design system legitimately aligns colours on
-    purpose ("Success = Moss, by design"), and a generator that rejected that
+    purpose (one palette entry defined as equal to another), and a generator
+    that rejected that
     would be wrong about the operator's intent.
 
     Compares the BASE value only. Two tokens agreeing in one mode and diverging