The verify-on-stop guard fired too eagerly — including on doc/markdown/skill
edits with nothing to verify, where it pushed a pointless /tmp verification
script. Three changes:
1. Default OFF for new installs: agent.verify_on_stop defaults to false
(was the "auto" surface-aware sentinel). _config_version bumped 30 -> 31.
2. One-time migration (v30 -> v31): existing installs are switched off once,
but only when the value is missing or still the "auto" sentinel — an
explicit true/false the user set is preserved.
3. Path filter: build_verify_on_stop_nudge() now drops documentation/prose
paths (.md/.mdx/.rst/.txt/LICENSE/CHANGELOG/...) so even when explicitly
enabled, a doc-only turn never nudges. Mixed doc+code turns still nudge on
the code paths.
The legacy "auto" sentinel is still honored when set explicitly (ON for
interactive coding surfaces, OFF for messaging). HERMES_VERIFY_ON_STOP env
override unchanged.