playbook run --help says --allow-shell implies --yes; the runtime requires both flags

[explosivebit]

What is wrong

The help text and the runtime disagree about the shell-exec security gate on playbook run.

Help text (clap registry, crates/forgeplan-cli/src/main.rs:984-988):

--allow-shell ... default-deny gate for the CWE-78 surface. Implies --yes. Alternative:
set [playbook] allow_shell = true in workspace config.yaml

Runtime (crates/forgeplan-cli/src/commands/playbook.rs:376): --yes is required independently of
--allow-shell. A non-dry-run without it exits 2 with
playbook run requires --yes confirmation (ADR-009 security gate).

The doc comment directly above that function (playbook.rs:360-367) records the PROB-053 audit
Round 7 decision to keep the two flags independent - the earlier let yes = yes || allow_shell
shadow collapsed two distinct risk acknowledgements into one toggle. The help string was not
updated when the shadow was removed.

Evidence

• help string: main.rs:984-988; runtime gate: playbook.rs:376; rationale: playbook.rs:360-367
• shell permission is decided solely by self.config.allow_shell
  (crates/forgeplan-core/src/playbook/executor.rs:306), and the dispatcher takes a single
  allow_shell: bool (crates/forgeplan-core/src/playbook/dispatch/mod.rs:215)
• website/src/content/docs/docs/cli/playbook-run.md documents the runtime behaviour and flags the
  help-text discrepancy rather than repeating the claim

Fix

Either drop "Implies --yes" from the flag description, or restore the implication. Given the
Round 7 rationale, dropping it matches the intent: two flags, two acknowledgements.

Revisit trigger

Act before any release whose notes mention the playbook security gate - the wrong sentence is the
one a user reads when deciding whether their invocation is safe.