Add ordered mouse press drain API

[ogyrec-o]

Summary

Adds a bounded ordered mouse press drain API to ClientInputProvider.

Why

frevenengine/freven-engine#386 smoke found that rapid terrain interactions still miss actions after the prediction/reconciliation fixes:

• double RMB can produce only one submitted action
• LMB -> RMB in the same tick can miss RMB
• Vanilla currently consumes Left first and Right only through else if
• existing SDK input API exposes per-button boolean/consume semantics, not ordered press events

Engine investigation showed this cannot be fixed correctly with a private engine-only API because Vanilla/mods need the public SDK trait.

What changed

• Adds ClientMouseButtonPress.
• Adds ClientInputProvider::drain_mouse_button_presses(owner, limit).
• Documents ordered, bounded drain semantics:
  • preserves cross-button order
  • preserves repeated same-button clicks
  • respects caller-provided limit
  • keeps owner/binding guard semantics
• Keeps existing mouse_button_just_pressed and consume_mouse_button_press APIs unchanged.
• Default implementation returns an empty vector for source compatibility with existing providers.
• Updates WASM authoring docs to mention the new ordered drain API.

Tests

Adds coverage for:

• double RMB represented as two press events
• LMB then RMB order
• RMB then LMB order
• explicit drain limit
• owner/binding guard behavior
• legacy consume API compatibility
• legacy consume API limitation for ordered multi-button drains

Boundaries

• no engine changes
• no Vanilla changes
• no Boot changes
• no server authority changes
• no client prediction as authority
• no held-button spam substitute

Validation

• cargo +stable fmt --all -- --check
• cargo +stable test --locked -p freven_avatar_sdk_types input
• cargo +stable test --locked --workspace
• cargo +stable clippy --locked --workspace --all-targets -- -D warnings
• cargo +stable clippy --locked --workspace --all-targets --all-features -- -D warnings
• git --no-pager diff --check

Related:

• frevenengine/freven-engine#386
• frevenengine/freven-engine#394
• Allow dependent terrain prediction admission freven-vanilla#80
• frevenengine/freven-engine#348