fix: respect Ctrl as the primary modifier on Windows/Linux

[mthorme]

Problem

On Windows (and Linux), several interactions were dead because the handlers gated on event.metaKey directly. Off macOS, metaKey is the Super/Win key, not Ctrl — so the Cmd-equivalent actions never fired, and a number of on-screen hints still showed ⌘.

The shortcut registry is already cross-platform (matchesShortcut maps mod → Ctrl off macOS). The bugs were all in raw handlers that bypass it.

What this fixes

• Create Task: Ctrl+Enter / Ctrl+Shift+Enter now create the task (was metaKey-only).
• Terminal: Ctrl+Click opens URLs and file paths (browser / editor / external), matching Cmd+Click on macOS.
• Kanban board & list: Ctrl+Click opens a task in the background.
• Hints: hardcoded ⌘ strings now render Ctrl off macOS via formatKeysForDisplay (Create button, terminal hover hints). The terminal context menu now shows the real Ctrl+Shift+C / Ctrl+Shift+V copy-paste bindings on Windows/Linux instead of ⌘C / ⌘V.

Approach

Add a small isPrimaryModifier(e) helper to @slayzone/shortcuts (re-exported from @slayzone/ui) that returns metaKey on macOS and ctrlKey elsewhere — the same mod semantics the registry uses, but usable from raw mouse/keyboard handlers. Modifier normalization happens at the click boundary so downstream logic is untouched. Also added an enter → ↩ entry to the display maps so formatKeysForDisplay can render the submit hints.

No macOS behavior changes (on mac isPrimaryModifier === metaKey).

Testing

• pnpm typecheck ✅
• pnpm lint:theme ✅
• pnpm build ✅
• pnpm --filter @slayzone/shortcuts test — added unit tests for isPrimaryModifier; no new failures.

🤖 Generated with Claude Code

Greptile Summary

This PR makes primary-modifier shortcuts work consistently across macOS, Windows, and Linux. It changes:

• Adds isPrimaryModifier for raw keyboard and mouse handlers.
• Updates create-task, terminal-link, and kanban click handlers to use Ctrl off macOS.
• Replaces hardcoded Cmd hints with platform-aware shortcut labels.
• Adjusts terminal copy/paste and hover hints for Windows/Linux bindings.
• Adds shortcut tests for the new primary-modifier helper.

Confidence Score: 5/5

This looks safe to merge.

• No blocking issues found in the changed code.

_{Reviews (2): Last reviewed commit: "fix: address review on Windows shortcut ..." | Re-trigger Greptile}