feat(scope): --scope-file YAML loader + web Scoping/Guardrails UI

Hard scoping was already enforced in code (every request passes
ScopePolicy::check_request; exclude beats allowlist; capability token caps
it; out-of-scope findings withheld + audited). What was missing was a way to
author that boundary from a file or the web form instead of only CLI flags.

- scope.rs: ScopePolicy::from_yaml / from_file — a dependency-free parser for
  the friendly string format (app.example.com, *.wildcard, CIDR, url-prefix),
  the same strings Pattern::parse already takes, NOT the raw serde {kind,value}
  shape. Strict in one direction: an unreadable file errors, an empty hard list
  authorizes nothing (a safe failure, but the operator's choice, not a typo).
- CLI: --scope-file <yaml>. Loaded before authorization so --in-scope adds to
  it and the capability grant still caps it.
- Web: a full Scoping & Guardrails section in the Authorization tab — hard
  scope, exclusions, observe-only, destructive-method + account-creation
  toggles, max accounts, rate limit, forbidden payloads, notes. The server
  materializes a scope YAML and passes --scope-file; notes stay labelled
  "guidance, NOT enforced" so prose is never mistaken for a control.
- examples/scope.example.yaml documents the format.

End-to-end verified: web form -> YAML -> Rust loader -> enforced boundary.
332 tests (+4).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

README.md

@@ -717,6 +717,7 @@ git clone https://github.com/digininja/DVWA /tmp/DVWA
 | `--sandbox [image]` | Run agent commands in a Kali container (docker/podman) instead of on the host. |
 | `--revalidate-poc` | Re-run every PoC after validation; demote any that no longer reproduces. |
 | `--compliance pci-dss,hipaa,soc2` | Map findings onto compliance controls in the report. |
+| `--scope-file <yaml>` | Load the hard scope + guardrails from a YAML file (see `examples/scope.example.yaml`). Enforced in code; a capability token still caps it. |
 | `-v, --verbose` | Log each agent as it launches, recon, and votes. |
 
 ### Authentication — run via API key *or* subscription