feat: --quick economy preset for short, low-cost tests (CLI + REPL + web)

Billing concern: a full run with 2-3 voters, deep chaining and exhaustive recon
burns a lot of tokens. --quick is one switch for a fast, cheap pass:
one voter, one chain round, light recon (intensity 1), ≤6 agents, eco budget.
Dropping voting from 3 models to 1 is the biggest saver.

- CLI: --quick on run/whitebox/greybox (apply_quick, applied last so it wins)
- REPL: /quick (aliases /economy /eco), listed in help + completion
- web: ⚡ Quick-mode checkbox in the wizard -> /quick in the REPL script
- README: documented in the flags table
- 420 tests passing

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/server.js

@@ -821,6 +821,7 @@ function sanitizeLaunch(body) {
     name: body.name || '',
     sandbox: !!body.sandbox,
     typesafe: body.typesafe,
+    quick: !!body.quick,
   };
 }
 
@@ -842,6 +843,8 @@ function buildReplScript(body) {
   if (body.outOfScope) lines.push(`/scope-out ${body.outOfScope}`);
   if (body.creds) lines.push(`/creds ${body.creds}`);
   lines.push((body.agents || []).length ? `/only ${body.agents.join(',')}` : '/only clear');
+  // Economy preset last, so it wins over the per-knob settings above.
+  if (body.quick) lines.push('/quick');
   lines.push('/run');
   return lines;
 }