When display.personality is set in config.yaml (e.g. personality: taleb),
new sessions now inherit it automatically instead of starting with
personality=None and requiring an explicit /personality command.
This makes the selected personality sticky across new conversations rather
than requiring per-session activation.
Behavior:
- display.personality values 'none', 'default', 'neutral', '' are treated
as no personality (personality=None), matching TUI gateway semantics.
- Config read is wrapped in try/except — if it fails, personality falls
back to None (no crash, no regression).
- Case-insensitive: 'Taleb' normalizes to 'taleb'.
The /personality slash command still works for per-session overrides as
before; this change only affects the initial default.
AJV20