fix(curation): kill dev-artefact leak + rename agent honestly

Oracle remediation batch 1 — closing gaps #1 (agent overclaim), #4
(demo-data leak), #5 (raw-ID exposure):

- src/lib/flowCuration.ts: shared isDevArtefact + curatedPublishedFlows
  filter for the whole codebase. Patterns drop rv_/orphan/Atlas F1/MCP
  SDX/Codex Test/sidekick/process_<ts>/backfill/smoke/probe/fixture and
  the EA2_* internal source_contexts.
- src/scenes/Hub.tsx: loadPublishedFlows uses the shared curator
- src/lib/agentTools.ts: list_processes and start_process both use the
  shared curator; raw transaction_id no longer in start reply
- src/state/store.ts: snapshot + live merges curated; resolveDefaultStepId
  guards against scenarios whose defaultStepId references a stale step
- src/scenes/Wizard.tsx: 'Process definition <hex>' confirmation replaced
  with the user-facing process name
- src/scenes/Hub.tsx: start toast no longer shows transaction_id prefix
- src/scenes/Agent.tsx + App.tsx + Landing.tsx: rename Pi -> FlowMaster
  Command Assistant. Welcome message says explicitly that this is a
  deterministic router and the LLM agent + tenant memory are on the
  roadmap. Tab label, hub chip, turn author all rebranded.
- src/scenes/GeoAttendance.tsx: scene re-titled to 'Attendance map ·
  preview' with honest copy explaining the dataset is illustrative until
  the EA2 attendance feed is wired in.
- src/data/synthetic.ts: orphaned from runtime (kept in tree for tests).
  Snapshot now sources only the live-cached EA2 read (scenarios.json),
  filtered through the same curator.

29/29 tests green. No more 'rv test flow 0' / 'orphan' / 'Atlas F1' / raw
32-char hex IDs visible to a buyer.

src/scenes/Landing.tsx

@@ -80,7 +80,7 @@ export default function Landing() {
             <button className="hub-chip" onClick={() => setScene("hub-hr")}>People Hub</button>
             <button className="hub-chip" onClick={() => setScene("hub-it")}>IT Hub</button>
             <button className="hub-chip" onClick={() => setScene("geo-attendance")}>Attendance Map</button>
-            <button className="hub-chip" onClick={() => setScene("agent")}>Talk to Pi</button>
+            <button className="hub-chip" onClick={() => setScene("agent")}>Command Assistant</button>
             <button className="hub-chip" onClick={() => setScene("chat")}>Team Chat</button>
             <button className="hub-chip" onClick={() => setScene("explainer")}>What is FlowMaster?</button>
           </div>