Implement combat target selection and ARPG hit validation loop

[JOY]

Summary

Move the combat prototype toward ARPG-style attack validation where targets can move out of range.

Scope

• Add target selection or nearest valid target detection for the prototype.
• Validate range, cone, obstacle, target alive state, and attack timing server-side.
• Support hit, miss, out-of-range, blocked, and defeated result states.
• Keep client visuals responsive but non-authoritative.

Acceptance Criteria

• Attacking a target in range can apply server-validated damage.
• Attacking after the target moves out of range misses or is rejected.
• Client cannot submit negative damage or fake hit results.
• Hit result can drive animation feedback and HUD target HP.
• Backend tests cover valid hit, out-of-range, invalid target, and defeated target branches.

References

• ROADMAP.md
• docs/ARCHITECTURE.md

[JOY]

Implemented a scoped #147 targeting feedback pass on dev:

• The prototype training target now shows target-selection preview state before attack submission.
• The target plate highlights Target ready when the target is in valid range/cone/line, and shows compact miss states such as out of range, outside angle, blocked, or respawning when it is not hittable.
• PrototypeCombatTrainingHotkeys refreshes the preview at a throttled interval and still submits only server-validated hit requests to Nakama.
• Existing backend tests already cover valid hit, out-of-range, invalid value, defeated target, and reward ledger branches for secondspawn_combat_training_hit.
• Updated CHANGELOG.md.

Local review fallback: APPROVED WITH SUGGESTIONS. No blocking issue found. This keeps client targeting visual-only; authoritative hit/reward validation remains in Nakama.

Verification run:

• npm test in backend/nakama: pass
• npm run build in backend/nakama: pass
• markdownlint for public docs: pass
• git diff --check: pass
• touched-file em-dash scan: pass
• tools/windows/check-local-health.ps1 -Strict: pass exit; Unity compile OK, Editor.log tail clean, Nakama/Postgres OK, MCP 8080/8766 listening.

[JOY]

Implemented and merged in PR #170. Verification: Nakama npm ci, build, and tests passed; markdown lint passed; local code-review fallback approved; root Unity recompile completed with no C# errors; Play Mode smoke ran with no errors, only the known Visual Studio UDP messaging warning.