feat(agent): add pre_verify hook and verify-on-stop coding guidance

Add a `pre_verify` user/plugin/shell hook fired once per turn when the agent
edited code and is about to finish, after the existing verify-on-stop guard. A
hook can keep the agent going one more turn (run a check, defer it, tidy the
diff) by returning {"action":"continue","message":...} (the Claude-Code Stop
shape {"decision":"block","reason":...} is accepted too). Hooks receive coding,
attempt, final_response, and sorted changed_paths so they can self-scope and
self-throttle; the path is bounded by agent.max_verify_nudges and preserves
message-role alternation.

Hermes still ships its default coding guidance (agent.verify_guidance, on by
default), but it now rides the evidence-based verify-on-stop missing-evidence
nudge instead of a separate default pre_verify continuation, so it costs no
extra model turn of its own. Guidance reuses the shared utils.is_truthy_value
parser rather than a local copy.

cli-config.yaml.example

@@ -646,6 +646,17 @@ agent:
   # force it on or off; the HERMES_VERIFY_ON_STOP env var (1/0) takes precedence.
   # verify_on_stop: auto
 
+  # When verify-on-stop finds edited code without fresh verification evidence,
+  # append guidance for creative UI work (avoid broad tsc/lint/test before visual
+  # approval) and clean-diff expectations. Set false to keep that nudge terse.
+  # verify_guidance: true
+
+  # A `pre_verify` hook (plugin or shell, see Event Hooks docs) can keep the
+  # agent going one more turn to verify/clean before finishing. This caps how
+  # many times one turn may be nudged to continue, so a hook can't trap the loop.
+  # Default 3.
+  # max_verify_nudges: 3
+
   # Enable verbose logging
   verbose: false