Add "Copy file path" to file viewer pane right-click menu

[elviskahoro]

Closes #8974

What

Right-clicking inside a file opened in Warp's rendered file viewer (FileNotebookView, e.g. a markdown file) previously only offered the four split-pane options. This PR adds a "Copy file path" entry to that right-click context menu — the right-click portion requested in #8974 (the overflow-menu "Copy file path" already exists).

• Matches the wording already used in the pane's header overflow menu and copies the same display_path() string, so it works for both local and remote files.
• Scoped to file-backed panes: FileNotebookView sets the current file's path when the menu opens; regular notebooks never set it, so the item stays hidden there.

How

• app/src/notebooks/context_menu.rs — added copy_file_path state + setter to the shared ContextMenuState, the new menu item (inserted between the text-action and split-pane sections with correct separator handling), a ContextMenuAction::CopyFilePath variant, and a clipboard-write handler.
• app/src/notebooks/file/mod.rs — sets the open file's display_path() on the menu when it's opened.
• app/src/notebooks/context_menu_tests.rs — added test_copy_file_path_action covering: item present + separated when a text section exists, item leading the menu when the text section is empty, and item absent when no path is set.

Testing

• cargo check -p warp --lib → passes, no errors.
• cargo test -p warp --lib test_copy_file_path_action → passes.

[cla-bot]

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[oz-for-oss]

@elviskahoro

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[oz-for-oss]

@elviskahoro

Every PR must be linked to a same-repo issue before Oz can review it.

Next step: open or find a same-repo issue describing this change, then link it to this PR by adding Closes #123 to the PR description (or using the "Development" sidebar on GitHub). A maintainer will mark the issue ready-to-implement when it is ready. Once it is marked, comment /oz-review to re-trigger review.

See the contribution guidelines for the full readiness model.

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[elviskahoro]

@oz-agent This PR closes #8974

[elviskahoro]

@bholmesdev I did the CLA check! lmk if this needs feature flag