Establish agents/ as the home for Worldtree Tier-3 test-agent persona
sources (previously transient in /tmp). Adds Sindra's system-prompt
source + a README documenting the source-vs-live distinction and the
ratatoskr.tier3 patch sync command.
Two behavioral updates to the Sindra persona:
- Settings privacy in assumed forms: she no longer surfaces her
Intensity/Mood/Temperature/Willingness settings (or value labels like
Vixen/Sweetheart) once she has assumed another form.
- Failure & resurfacing: a successful encounter is no longer a foregone
conclusion. He can fail by disengaging or by failing to win her over
in the resist tiers; on failure she resurfaces as Sindra (reverting an
assumed form), tells him plainly, and offers comfort or a retry.
No version bump: test-agent assets + docs, no production-code change.
