needs-design: graduated cost to change the anima-ritual resonance (magical identity) — free-ish at level 1, harder as you rise

[TehomCD]

Ruling (Tehom, 2026-08-06, session on #2971)

The anima-ritual resonance is the character's magical identity — "the flavor of their
magic." It must be populated at CG (folded into #2971: finalize writes the mandatory CG
gift-resonance pick onto the anima ritual's RitualCheckConfig.resonance), and it
"should be something that can be changed relatively easily at level 1, but much less
easily as they rise."

Verified mechanism (2026-08-06)

• RitualCheckConfig.resonance (src/world/magic/models/ritual_check_config.py:52) —
  nullable FK, "Optional resonance filter for this ritual."
• The change surface already exists and is ungated:
  RitualCheckConfigPatchSerializer (src/world/magic/serializers.py:1193) accepts
  resonance_id on the ritual PATCH endpoint, so any player can change it freely at
  any level today. There is no cost, no check, no level gate.
• After An empty gift resonance set means 'unrestricted' at the gate but 'none available' to all four selectors, so authored gifts are granted with no thread #2971, CG populates the field for every new character, and the grant-time
  resonance resolver plus _resolve_moment_resonance (Dramatic Moment: fall back to the anima-ritual resonance when no thread resolves one #2970,
  src/world/magic/services/gain.py) read it as the character's "main" resonance —
  so changing it is now a meaningful identity change, not a cosmetic edit.

The design question

What does changing your anima-ritual resonance cost, and how does that cost scale with
advancement (level / path stage / thread depth)? Directional ruling above: cheap-or-free
at level 1, substantially harder later. Open sub-questions:

1. What currency/ceremony mediates the change (XP, resonance balance, a rite like the
   sanctum's Rite of Purging, a GM-adjacent event)?
2. What does "harder as they rise" key on — character level, highest thread level, path
   stage crossings?
3. Does changing it re-anchor anything downstream (existing GIFT threads keep their own
   resonance — presumably yes, untouched), or is it purely the identity/fallback seam?
4. Telnet + web parity for whatever the change flow becomes (the PATCH endpoint would
   gain the gate; a bare serializer edit must not bypass the cost).

Not asserted work — needs a design pass before any implementation.

Related: #2971 (CG population + resolver), #2970 (the main-resonance seam), ADR-0052.