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/App.tsx

@@ -80,7 +80,7 @@ export default function App() {
               <Bot size={13} /> Chat
             </button>
             <button role="tab" aria-selected={scene === "agent"} className={`tab${scene === "agent" ? " tab-sel" : ""}`} onClick={() => setScene("agent")}>
-              <Bot size={13} /> Pi
+              <Bot size={13} /> Assistant
             </button>
             <button role="tab" aria-selected={scene === "settings"} className={`tab${scene === "settings" ? " tab-sel" : ""}`} onClick={() => setScene("settings")}>
               <Cog size={13} /> Settings