Support Purpur 26.1.2 in 26.x version resolution

[Copilot]

Codex currently rejects Purpur 26.1.2 during static version detection with Unexpected version: 26.1.2, preventing plugin startup despite 26.2 already being supported. This change aligns 26.1.2 handling with existing 26.2 behavior across version detection and NMS package resolution.

• Version enum mapping (codex-api/core/Version.java)

  • Added 26.1.2 and 26.1.2-R0.1-SNAPSHOT to the V26_R1 switch branch (same as 26.2).

• NMS package mapping (codex-api/compat/VersionManager.java)

  • Added 26.1.2 to getPackageFromVersion(...) so it resolves to v26_2 (same as 26.2).

• Focused regression test (codex-api/.../VersionManagerTest.java)

  • Added a targeted test asserting 26.1.2 -> v26_2.

// Version.java
case "26.1.2-R0.1-SNAPSHOT", "26.1.2", "26.2-R0.1-SNAPSHOT", "26.2" -> Version.V26_R1;

// VersionManager.java
case "26.1.2", "26.2" -> "v26_2";

[MaksyKun]

@copilot Please revert:

• fbf1ba6
• 6473315
• 739ee42

[Copilot]

@copilot Please revert:

• fbf1ba6
• [6473315](Add Simplified Chinese translation #14...

Done in commit 0d90340: reverted fbf1ba6, 6473315, and 739ee42 as requested.