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>

README.md

@@ -846,6 +846,7 @@ git clone https://github.com/digininja/DVWA /tmp/DVWA
 | `--model provider:model` | Repeatable. First = primary; the rest fail over **and** form the voting jury. |
 | `--subscription` | Use the local CLI login (Claude/Codex/Gemini/Grok) instead of an API key. |
 | `--mcp` | Enable Playwright MCP (auto-provisioned via `npx`; backends without MCP use built-in tools). |
+| `--quick` | **Economy preset for a short, low-cost test** — one voter, one chain round, light recon, ≤6 agents, `eco` budget. The single switch for a fast, cheap pass; dropping voting to one model is the biggest token saver. (REPL: `/quick`; web: the ⚡ Quick-mode checkbox.) |
 | `--vote-n N` | How many models must agree a finding is real (default 3 / 2 for whitebox). |
 | `--max-agents N` | Cap agents run (`0` = all matching the recon). |
 | `--offline` | Exercise the full pipeline without calling any model. |