Add Atavism 10.13 Combat SQL reference set and documentation index cleanup

[Copilot]

This PR delivers the next SQL documentation reference pass for Mystical Islands’ Combat Module using the current Atavism 10.13 structure. It adds plugin-level combat references, a wiki/source-of-truth index page, and aligns top-level docs to the current docs/sql/10.13/* + docs/sql/reference/* layout.

• Combat Module reference coverage

  • Added:
    • docs/sql/reference/combat-arena-plugin.md
    • docs/sql/reference/combat-skills-plugin.md
    • docs/sql/reference/combat-abilities-plugin.md
    • docs/sql/reference/combat-effects-plugin.md
    • docs/sql/reference/combat-coordinated-effects-plugin.md
    • docs/sql/reference/combat-stats-plugin.md
    • docs/sql/reference/combat-damage-plugin.md
    • docs/sql/reference/combat-stat-thresholds.md
  • Each file follows a consistent AI-ready structure: purpose, source links, reviewed SQL sources, table usage, column mapping table, relationships, dependency-ordered data flow, non-production SQL planning example, Mystical Islands usage notes, and uncertainty markers.

• AI/database master references

  • Added docs/sql/reference/atavism-wiki-index-reference.md to formalize wiki usage and schema authority rules.
  • Added/updated docs/sql/reference/ai-database-and-server-reference.md as a single handoff page for AI assistants and developers.

• Reference index and navigation updates

  • Updated docs/sql/reference/README.md with a full Combat Module section and links to the new wiki/index references.
  • Updated root README.md and docs/README.md to include direct links to:
    • docs/sql/reference/README.md
    • docs/sql/reference/ai-database-and-server-reference.md
    • docs/sql/reference/atavism-wiki-index-reference.md

• Legacy/stale documentation cleanup

  • Clarified docs/database-reference.md as legacy Atavism 10.9 archive content and redirected current SQL work to the 10.13 reference library.
  • Removed stale ambiguity around documentation/source-of-truth locations by standardizing references on current docs/ paths.

Example snippet introduced in the new combat references (non-production planning pattern):

-- Example only. Verify IDs before inserting.
INSERT INTO damage_type (name, resistance_stat, power_stat, accuracy_stat, evasion_stat, critic_chance_stat, critic_power_stat, isactive)
VALUES ('storm', 'storm_resistance', 'storm_power', 'storm_accuracy', 'storm_evasion', 'storm_crit', 'storm_crit_power', 1);