Add contextual world-item interaction hints

[valzargaming]

World-item selection and pickup were documented in Controls help but absent from the current-item caption. Add one wrapping hint row to the existing opt-in card: mouse hover describes selection and double-click pickup request; selected context describes pickup; keyboard/controller and unbound input reflect the current binding. Exact observed identity/details, neutral unknown role, and host eligibility/outcome uncertainty remain intact.

Validation at head c8124ef:

• Windows Godot 4.7.2 import/startup, paid no-port actual-shell context fixture, world inventory preview and selected-target controls passed locally. Includes hovered/selected 640px and 1440px cards, remaps/unbound input, default-off captions, reset/rebuild/disconnect, unchanged geometry/canonical snapshot, stable pickup IDs and pending unknown state.
• Full Windows/Linux Godot, PHP, development exports and CI required passed: https://github.com/Valgorithms/Frontier-Systems/actions/runs/38189273142
• Windows/Linux inventory preview passed: https://github.com/Valgorithms/Frontier-Systems/actions/runs/38189273139
• Tested synthetic commit: 32c3664, confirmed by both platform build artifact names.

No stills needed for this scoped change; human/controller hardware/VR/Linux graphical acceptance was not exercised. No video, media uploads, self-merge, release or deployment. Draft retained for coordinator review. Managed worktree remains clean and available.

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