The op-* crate reorg never ran `cargo clippy -- -D warnings`, so the CI
lint gate failed. Fix every violation surgically: real fixes for
mechanical lints (needless_range_loop, derivable_impls, ptr_arg,
needless_borrow, doc_lazy_continuation, unused_imports, manual_find,
collapsible_match, never_loop, dead_code, complex types via type
aliases) and scoped `#[allow]` for intrusive ones (too_many_arguments
on paint helpers, result_large_err where ToolOutcome / PenNode payloads
are deliberately the Err type).
Phase 7.3 strangler reorg — rename the web widget host crate to the
op- prefix. The crate's openpencil-shell-core dependency is repointed
to op-editor-ui (the real source crate for the widget facade / theme
/ layout scene / scene vars / render-backend / gesture types).
- crate name: openpencil-shell-web -> op-host-web
- lib name: openpencil_shell_web -> op_host_web
- every openpencil_shell_core:: path -> op_editor_ui::
- native skia.rs include_bytes! path follows the moved assets dir
- smoke harness + lib doc-comment refs updated
