feat: batch of capability tools (asset import, references, mesh, physics, particle, material, project/undo/component/lighting/timeline/dialog)

[dehuaichendragonplus]

Why

Driving Unity through this MCP, an agent repeatedly hits operations with no dedicated tool and has to hand-roll execute_code for them: reading/writing importer settings, asking "what references this asset", inspecting a mesh, casting a physics ray, reading material shader props, undo, etc. These are common, fiddly, and error-prone to re-derive each time. This PR adds dedicated, structured-output tools for that gap (backlog "capability" set), so the common cases are one reliable call.

Approach

12 new self-contained [ToolProvider] files under Editor/Tools/Builtins/, following the existing conventions:

• Each tool returns object via Response.Success(msg, data) / Response.Error(CODE, data) — the same {success, ...} envelope the rest of the surface uses.
• Scene targets resolve through ObjectsHelper (name / hierarchy path / instance id, inactive included); assets through AssetDatabase.
• Read tools are [ReadOnlyTool]; mutating tools are [SceneEditingTool] and use Undo where the operation is undoable.
• Optional-package types (Timeline) are accessed purely by reflection, so the package compiles without a com.unity.timeline asmdef reference and degrades to a clear error when absent.

New tools

Provider	Tools
AssetImport	get_asset_import_settings, set_asset_import_settings
References	find_references, find_broken_references
Mesh	get_mesh_info
Physics	physics_raycast, physics_overlap, physics2d_overlap_point
Particle	particle_control
Material	get_material_properties, set_material_property
ProjectSettings	get_project_settings, get_editor_pref
Undo	undo, redo, get_undo_state
ComponentBatch	copy_component, paste_component_values, add_component_to_many
Lighting	get_lighting_settings, set_lighting_settings, bake_lightmaps
Timeline	director_evaluate (reflection-based)
Dialog	list_open_dialogs, dismiss_dialog

Test results

Verified in a Unity 6000.3.13f1 project (embedded package, compiles with zero errors). Every tool was exercised and returns a proper structured envelope; highlights:

• get_asset_import_settings reads full Texture importer fields; set_... round-trips and reads applied values back.
• find_references reverse-scanned 19,085 project assets and correctly found the referencing asset; per-direction truncated flags reported.
• get_mesh_info → 24 verts / 12 tris / UV channels on a cube; physics_raycast/overlap hit the expected collider; particle_control simulate froze a VFX at a fixed time; director_evaluate returns a clean PLAYABLE_DIRECTOR_NOT_FOUND when no director is bound.
• copy_component/paste_component_values/add_component_to_many per-target results verified; undo/redo round-trip verified.
• dismiss_dialog refuses to close docked panels (Inspector/Console) and only acts on floating/utility windows.

The whole set then went through an adversarial multi-angle code review; 15 findings were fixed and the affected tools re-tested through the live MCP interface (malformed args now return INVALID_PARAM instead of silent wrong writes; oversized captures spill to file; particle_control clamps simulate time; physics queries SyncTransforms first; lighting validates enum/color; component paste-as-new is undo-tracked; etc.).

Compatibility

• All new tools sit at the tool-call layer over the existing MCP protocol — no wire-protocol, initialize, or transport change → compatible with every MCP client (Claude Code, Cursor, LM Studio, VS Code, Trae, Kiro, Codex).
• All new files; no existing file is modified, so there is no interaction with other in-flight PRs.
• Timeline support is reflection-only (no new package dependency); every other tool uses core engine/editor APIs verified present and non-obsolete on 6000.3.13f1.

Checklist

• Tested in a clean Unity 2022.3+ project (Unity 6000.3.13f1)
• Verified Funplay > MCP Server opens and starts correctly
• Did not commit local junk such as .idea/ or .DS_Store
• Updated CHANGELOG.md