Fixes#1804, fixes#1962
The migration entry 'gpt-5.2-codex → gpt-5.3-codex' caused the plugin to silently overwrite user configs on every startup with a model that doesn't exist in the OpenAI API. Users explicitly setting gpt-5.2-codex (the correct current model) were forced to revert their config manually every session.
Move hashline_edit out of experimental so it is a stable top-level config with default-on runtime behavior and explicit disable support. Add migration and tests to preserve existing experimental.hashline_edit users without breaking configs.
Shorter hook name, disableable via disabled_hooks config, migration added
for backward compatibility. Also forces agent switch to Hephaestus on
Sisyphus + GPT detection. Docs updated with new hook name.
Migration changes were only applied to rawConfig if file write succeeded,
leaving the running process on stale config. Also stops logging backup
path when the backup copy itself failed.
Previously, migrateConfigFile() mutated rawConfig directly. If the file
write failed (e.g. read-only file, permissions), the in-memory config was
already changed to the migrated values, causing the plugin to use migrated
models even though the user's file was untouched. On the next run, the
migration would fire again since _migrations was never persisted.
Now all mutations happen on a structuredClone copy. The original rawConfig
is only updated after the file write succeeds. If the write fails,
rawConfig stays untouched and the function returns false.
