fix(pact-system): resolve 5 spec-vs-code discrepancies (DISC-4,6,8,11,12)

- DISC-11: Fix floor 140/150 element composition in guardian-data.ts
  Floor 140 now uses [light, fire, radiantflames] (was [sand, earth, water])
  Floor 150 now uses [air, death, miasma] (was [lightning, fire, air])
- DISC-12: Reconcile spec §7.1 vs §8.2 tables in pact-system-spec.md
  Updated §8.2 to match §7.1 authoritative element mappings
- DISC-4: Deduplicate pact ritual completion logic
  Refactored pact-ritual.ts pipeline to delegate completion to
  prestigeStore.completePactRitual() instead of duplicating state writes
- DISC-6: Add 4 missing boon types to guardians
  critChance (floor 90), manaGain (floor 110), prestigeInsight (floor 200),
  studySpeed (floor 220) — all 12 spec boon types now used
- DISC-8: Add comment clarifying signedPactDetails persistence
  Code already correct (not reset by startNewLoop/resetPrestigeForNewLoop)
- Updated spire-utils.test.ts to match corrected floor 140/150 elements

docs/specs/attunements/invoker/systems/pact-system-spec.md

@@ -259,8 +259,8 @@ guardian's `unlocksMana` is derived from `resolveMultiUnlockChain(element)`:
 | 110 | lightning | `fire`, `air`, `lightning` |
 | 120 | frost | `air`, `water`, `frost` |
 | 130 | blackflame | `fire`, `earth`, `metal` |
-| 140 | radiantflames | `light`, `fire` |
-| 150 | miasma | `air`, `death` |
+| 140 | radiantflames | `light`, `fire`, `radiantflames` |
+| 150 | miasma | `air`, `death`, `miasma` |
 | 160 | shadowglass | `earth`, `dark` |
 | 170+ | exotic | varies (see guardian-data.ts) |
 
@@ -298,8 +298,8 @@ mana to any elemental type. All elemental mana must come from:
 | 110 | lightning | 22% | 13h |
 | 120 | frost | 28% | 14h |
 | 130 | blackflame | 32% | 15h |
-| 140 | sand+earth+water | 25% | 16h |
-| 150 | lightning+fire+air | 28% | 17h |
+| 140 | light+fire+radiantflames | 25% | 16h |
+| 150 | air+death+miasma | 28% | 17h |
 | 160 | shadowglass | 33% | 18h |
 
 ### 8.3 Tier 3 — Exotic Elements (Floors 170–240)