Use case-insensitive substring tag matching for todo and note filters

[multiplex55]

Motivation

• Improve tag matching so partial tag queries match tag variants (e.g., #rs matches rs3) and make matching case-insensitive.
• Allow @ as an alternative prefix to # in todo edit tag filters so users can query consistently with other commands.

Description

• Updated src/plugins/todo.rs to accept @ as well as # in the todo edit tag branch and to use case-insensitive substring matching when filtering tags in both the todo edit and todo list include/exclude tag branches by using to_lowercase().contains(...) comparisons.
• Updated src/plugins/note.rs note list branch to replace strict equality checks with case-insensitive substring checks for both include and exclude tag filters while keeping parse_query_filters invoked with &["@", "#", "tag:"] prefixes.
• Added/updated tests: expanded tests/todo_plugin.rs::list_filters_by_tag to cover todo list #rs, todo list @wor, and a negated partial filter todo list !#ui; added src/plugins/note.rs::note_list_supports_partial_tag_filters to cover note list #test, note list @ui, and a negated partial tag case.

Testing

• Attempted cargo test list_filters_by_tag; the build started but failed during the build of a dependency (alsa-sys) due to a missing system library (alsa) / pkg-config configuration, so the tests did not run to completion.
• Initially attempted cargo test list_filters_by_tag note_list_supports_partial_tag_filters which was an invalid cargo invocation and produced an argument error before rerunning the tests correctly.
• No unit tests completed successfully in this environment due to the external dependency build failure; tests added are named list_filters_by_tag and note_list_supports_partial_tag_filters and should pass in an environment with the required system libraries (or with the dependency disabled).

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Codex Task