fix(content): repair client consumers broken by the Duncarrow purge

The purge plan assumed content/world/** was pure build output. The client
reads it: content_db.gd loads content/world/topics/ (now absent, since every
topic was Duncarrow-generated) and its tests asserted on deleted ids.

- content_db: a missing content dir is an empty dir, not an error (§13)
- test_content_db: repoint at cosmology canon; drop deleted npc.mera-fenn
- test_content_db: assert the no-body-on-client invariant structurally, so it
  cannot pass vacuously when the topic set is empty
- schema.md: finish repointing the worked example onto specimen.md's ids
- restore a local real-bible --check smoke test (was only in CI)
- roadmap: record that generated content has client consumers

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.claude/skills/world-building/references/schema.md

@@ -142,7 +142,7 @@ build failure.
 A guarded fisherman who warms up and, if trusted, names who really owns the boats.
 
 ```yaml
-id: person.old-teague
+id: person.specimen-teague
 type: person
 status: canon
 secrecy: 0
@@ -153,37 +153,37 @@ body: >
 ```
 
 ```yaml
-id: fact.foreign-coin-on-the-docks
+id: fact.specimen-foreign-coin
 type: fact
 status: canon
 secrecy: 2
-related: [place.specimen-wharf, person.old-teague]
+related: [place.specimen-wharf, person.specimen-teague]
 body: >
   The dock hands are paid in pass-country coin, not town mint. Someone outside the
   charter is buying the wharf's silence, a little at a time.
 ```
 
 ```yaml
-id: npc.old-teague
+id: npc.specimen-teague
 type: person
 status: canon
 start_disposition: cold
-related: [person.old-teague, fact.foreign-coin-on-the-docks]
+related: [person.specimen-teague, fact.specimen-foreign-coin]
 body: >
-  Same man as person.old-teague; his interactive layer. Curt with strangers, not
+  Same man as person.specimen-teague; his interactive layer. Curt with strangers, not
   from malice but from a lifetime of watching talkers end up face-down in the
   river. Warms slowly, and when he does the dryness turns to something almost
   fond.
 
 knows:
-  - {fact: fact.foreign-coin-on-the-docks, gate: warm}
+  - {fact: fact.specimen-foreign-coin, gate: warm}
 
 disposition_notes: >
   Starts cold. Buying his catch, not his story, is what moves him. At warm he
   names the coin; he never speculates aloud about who mints it.
 ```
 
-Note: `person.old-teague` (secrecy 0, public) and `npc.old-teague` (the layer,
+Note: `person.specimen-teague` (secrecy 0, public) and `npc.specimen-teague` (the layer,
 persona server-only) are two entries. The fact is secrecy 2, gated at `warm`.
 
 ## Hand-authored JSON