`TtsrManager` previously ignored the `ttsr.enabled: false` toggle:
- `addRule()` still registered rules, so `bucketRules` demoted them
to the TTSR bucket and dropped the rulebook/alwaysApply fallback
- `hasRules()` still returned true, so `AgentSession` entered the
TTSR matching path on every message_update
- `checkDelta` / `checkSnapshot` (via `#matchBuffer`) still matched
patterns and could abort the stream and inject system reminders
Gate all three public-ish entry points on `#settings.enabled` so
disabling TTSR short-circuits the whole path. Condition rules fall
through to the rulebook bucket in `bucketRules` instead of being
silently swallowed.
Closes#1767
QianYan-Art
55c4efec4e