feat: add prestige system and skill upgrades with comprehensive documentation

docs/task5_insight_proposals.md

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+# Task 5: Insight Upgrade Proposals
+
+## Overview
+These proposals expand the existing Insight upgrade tree with permanent cross-loop advantages that accelerate early-loop ramp-up, aligned with the prestige philosophy defined in `docs/GAME_BRIEFING.md`. Proposals are grouped by thematic category, each with a rationale explaining alignment with core philosophy and gaps addressed in the existing upgrade tree (referenced below).
+
+### Existing Insight Upgrades (Reference)
+| Upgrade | Max Level | Cost (Insight/Level) | Effect |
+|---------|-----------|------------------------|--------|
+| Mana Well | 5 | 500 | +500 starting max mana |
+| Mana Flow | 10 | 750 | +0.5 permanent regen per level |
+| Deep Memory | 5 | 1000 | +1 memory slot per level |
+| Insight Amp | 4 | 1500 | +25% insight gain per level |
+| Spire Key | 5 | 4000 | Start at floor +2 per level |
+| Temporal Echo | 5 | 3000 | +10% mana generation per level |
+| Steady Hand | 5 | 1200 | -15% durability loss per level |
+| Ancient Knowledge | 5 | 2000 | Start with blueprint per level |
+| Elemental Attune | 10 | 600 | +25 element cap per level |
+| Spell Memory | 3 | 2500 | Start with random spell per level |
+| Guardian Pact | 5 | 3500 | +10% pact multiplier per level |
+| Quick Start | 3 | 400 | +100 starting mana per level |
+| Elem. Start | 3 | 800 | +5 each unlocked element per level |
+
+---
+
+## Theme 1: Mana & Elemental Acceleration
+### Rationale
+Existing upgrades in this category (Mana Well, Mana Flow, Elemental Attune, Elem. Start, Temporal Echo) focus on boosting mana generation and elemental access, but leave two critical gaps: (1) no permanent bonus to base capacity for unlocked mana types, and (2) no reduction to attunement conversion costs. These proposals fill those gaps to further reduce early-loop grind for elemental mana setup, a core bottleneck in first-loop progression.
+
+### Proposal 1: Unlocked Mana Type Capacity
+- **Max Level**: 5
+- **Cost**: 1000 Insight per level
+- **Effect**: Start each loop with +10 base capacity per unlocked mana type per level, plus immediate access to all mana types unlocked in any previous loop (no re-unlocking required).
+- **Gap Addressed**: Builds on `Elem. Start` (which grants +5 element cap per level) by adding permanent capacity for all historically unlocked types, eliminating repetitive base capacity grinding for each elemental mana type in early loop.
+- **Implementation Notes**:
+  - Track unlocked mana types across loops in cross-loop save data (`player.insight.unlockedManaTypes`)
+  - Apply capacity bonus on loop initialization via `LoopManager.applyInsightUpgrades()`
+  - Respect existing elemental cap limits from `Elemental Attune` upgrades
+
+### Proposal 2: Attunement Efficiency
+- **Max Level**: 5
+- **Cost**: 800 Insight per level
+- **Effect**: Reduce raw mana cost for elemental mana conversion (attunement) by 5% per level for the first 3 in-loop days.
+- **Gap Addressed**: Existing `Temporal Echo` boosts mana generation but not conversion efficiency. This directly accelerates early elemental mana accumulation, a key bottleneck in first 48 hours of each loop.
+- **Implementation Notes**:
+  - Apply cost reduction modifier to `AttunementStation` component for 72 in-loop hours
+  - Reset modifier automatically after 3-day window
+  - Stack with `Temporal Echo` generation bonuses
+
+---
+
+## Theme 2: Spire Progression Acceleration
+### Rationale
+Existing `Spire Key` (start at +2 floors per level) enables batch-skipping of low-level Spire floors, but lacks granular progression retention. This theme adds finer-grained Spire skip options to let players incrementally bypass repetitive early floors without over-skipping content, aligning with early-loop ramp-up goals.
+
+### Proposal 3: Spire Progress Retention
+- **Max Level**: 10
+- **Cost**: 500 Insight per level
+- **Effect**: Start each loop with 1 additional Spire floor cleared per level (stacks additively with `Spire Key` bonuses).
+- **Gap Addressed**: `Spire Key` only offers +2 floors per level, leaving no option for 1-floor increments. This allows players to tailor skip amount to their progression speed.
+- **Implementation Notes**:
+  - Store highest Spire floor reached per loop in `player.insight.highestSpireFloor`
+  - Apply cleared floors on new loop initialization via `SpireManager.syncProgress()`
+  - Cap total skipped floors at 50 (to prevent over-skipping endgame content)
+
+---
+
+## Theme 3: Guardian & Pact Continuity
+### Rationale
+Existing `Guardian Pact` boosts pact multipliers per level, but requires players to re-sign Guardian pacts each loop to access boons. This theme adds permanent pact memory to retain critical boons across loops, eliminating repetitive pact signing grind.
+
+### Proposal 4: Guardian Pact Memory
+- **Max Level**: 3
+- **Cost**: 3000 Insight per level
+- **Effect**: Retain 1 Guardian pact bonus (selected from previous loop's signed pacts) per level across loops, no re-signing required.
+- **Gap Addressed**: `Guardian Pact` only boosts multiplier strength, not retention. This lets players keep high-value boons (e.g., resource generation, damage resistance) permanently.
+- **Implementation Notes**:
+  - Track signed Guardian pacts per loop in `player.insight.signedGuardians`
+  - Add pact selection UI to prestige screen (`PrestigeModal.tsx`)
+  - Apply retained bonuses on loop start via `GuardianManager.applyRetainedPacts()`
+
+---
+
+## Theme 4: Skill & Knowledge Acceleration
+### Rationale
+Existing upgrades like `Ancient Knowledge` (blueprints), `Spell Memory` (spells), and `Quick Start` (starting mana) accelerate early knowledge/skill access, but leave a gap in core skill category progression. This theme adds skill head-start options to reduce early-game grind for core skill bonuses.
+
+### Proposal 5: Skill Head-Start
+- **Max Level**: 5
+- **Cost**: 600 Insight per level
+- **Effect**: Start each loop with 1 level in a chosen core skill category (mana, study, enchant, combat) per level, selectable during prestige.
+- **Gap Addressed**: No existing upgrade boosts core skill levels at loop start. Builds on `Quick Start`'s immediate resource boost by adding skill progression acceleration.
+- **Implementation Notes**:
+  - Add skill category selector to prestige UI (`PrestigeModal.tsx`)
+  - Apply skill levels on loop initialization via `SkillManager.addLevels()`
+  - Respect per-skill max level caps defined in `skillData.ts`