Generate Clipboard Modify help from catalogs

[multiplex55]

Motivation

• Replace a maintained static help list with generated, discoverable help derived from the existing Clipboard Modify registries so help always matches the executable catalog and user templates/pipelines.
• Make the dialog Help searchable and updateable after configuration reloads so custom templates and saved pipelines appear dynamically.
• Improve launcher result descriptions so actions (open section, partial completions, immediate execution, templates/pipelines, undo, and syntax errors) show clear, actionable text.
• Surface complete documentation for Clipboard Modify (catalog, syntax, schema, behavior and recovery) next to the project README.

Description

• Add a help-data builder at src/clipboard_modify/help.rs that produces HelpEntry items from operations() metadata plus current ClipboardModifierCatalog templates and pipelines, exposing canonical syntax, description, aliases, arguments, examples, category, and pipeline eligibility.
• Wire generated help into the dialog UI by adding a help_filter field and a help_ui renderer in src/gui/clipboard_modify_dialog.rs that replaces the previous static Help content with case-insensitive searchable entries sourced from build_help_entries().
• Improve launcher result descriptions in src/plugins/clipboard_modify.rs so section-open actions, partial completions, execution actions, template/pipeline executions, undo, and invalid-syntax actions present explicit, user-facing descriptions and parser hints.
• Register the help module in the clipboard_modify façade by updating src/clipboard_modify.rs to expose the new help API and add docs/clipboard_modify.md with the operation catalog, examples, schema and behavior notes, and update README.md with discoverability and examples.
• Add unit/regression tests in src/clipboard_modify/help.rs to assert every registered operation is included and that aliases/examples/templates/pipelines surface dynamically, and extend src/plugins/clipboard_modify.rs tests to assert contextual launcher descriptions.

Testing

• Ran cargo fmt and git diff --check, both passed without issues.
• Attempted cargo test clipboard_modify --lib, but the build failed due to a missing system dependency for alsa-sys (pkg-config/alsa.pc) in the environment, blocking full test execution.
• Attempted targeted help tests with cargo test --no-default-features clipboard_modify::help --lib, but this was also blocked by the same missing system alsa pkg-config metadata, so the new tests are present but not executed in this environment.

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Codex Task