fix: scope architect-guarded early-return to fix backward-compat regression

[Copilot]

Shell write enforcement had a gap: when no declared scope was present, bash/shell write paths skipped agent authority checks and could still mutate blocked targets (e.g. .swarm/evidence/*.json). This change aligns shell-write enforcement with write/edit/patch authority behavior so blocked zones remain blocked regardless of scope state.

• Root cause addressed: scope-only gate in shell write path

  • checkShellWriteScope(...) previously returned early when declaredScope was empty, which bypassed per-agent file authority evaluation for shell commands.

• Guardrail hardening in src/hooks/guardrails.ts

  • Enforce active-agent requirement for shell writes (fail closed when session has no active agent).
  • Apply universal deny-prefix checks to resolved shell write targets.
  • Run checkFileAuthorityWithRules(...) for each resolved shell write target before scope checks.
  • Keep declared-scope validation as an additional constraint (when scope exists), rather than the only constraint.

• Regression coverage in tests/unit/hooks/guardrails-shell-write.test.ts

  • Added architect-specific regression cases proving blocked behavior without declared scope:
    • redirection to .swarm/evidence/5.4.json
    • interpreter-eval write attempt via python3 -c ...

const authorityCheck = checkFileAuthorityWithRules(
  shellWriteAgent,
  write.resolvedPath,
  effectiveDirectory,
  precomputedAuthorityRules,
  { declaredScope },
);
if (!authorityCheck.allowed) {
  throw new Error(
    `WRITE BLOCKED: Agent "${shellWriteAgent}" is not authorised to write "${write.resolvedPath}" (via shell). Reason: ${authorityCheck.reason}`,
  );
}