add vanilla climbable movement parity

[Spencer0187]

Type of change

• Bug fix
• New feature
• Breaking change
• Refactor / code cleanup
• Performance improvement
• Chore / tooling
• Documentation

Summary

• Add vanilla 26.2 climbable movement handling using synchronized minecraft:climbable tags and the matching open-trapdoor-over-ladder rule.
• Apply vanilla velocity clamps, fall-distance reset, sneak/scaffolding behavior, and land/water climb impulses without duplicating block-shape or tag infrastructure.
• Depends on implement vanilla player attribute backend #602 and match vanilla player movement physics #610 (with generate vanilla 26.2 block state semantics #608 in match vanilla player movement physics #610's prerequisite stack) and is intended to merge only after those prerequisite PRs.

Reference

LivingEntity.java, Player.java, LocalPlayer.java, TrapDoorBlock.java, and VanillaBlockTagsProvider.java under reference/26.2/decompiled.

Testing

• just client-pre-pr after merging current upstream/master (530 client tests, 49 protocol tests, and 2 singleplayer tests passed)
• cargo clippy -p pomme-client --release --all-targets --no-default-features -- -D warnings via the pre-PR gate
• Manual in-game verification passed on the prerequisite-integrated climbable build for ladder ascent/slide/sneak behavior, waterlogged ladders, matching trapdoor continuation, fall-distance behavior, and representative vine-family climbing. The later upstream conflict resolution did not change climbable movement code.

Closes #619