feat: add eager extension activation for vim/neovim

[j4rviscmd]

Summary

Add coderm.extensions.eagerActivation setting to force immediate startup activation of specified extensions. This is critical for vim/neovim extensions where every millisecond of activation latency matters — without this, the first keystroke is handled by VS Code instead of the extension.

Changes

• New setting: coderm.extensions.eagerActivation (default: ["asvetliakov.vscode-neovim", "vscodevim.vim"])
• implicitActivationEvents.ts: Add setEagerExtensions() method; inject * activation event for listed extensions during _readActivationEvents()
• abstractExtensionService.ts: Read coderm.extensions.eagerActivation in constructor and pass to ImplicitActivationEvents
• eagerExtensions.ts: Register the new configuration setting
• coderm.contribution.ts: Import the new module
• README.md / README.ja.md: Add setting to the Coderm-specific settings table

How it works

AbstractExtensionService constructor
  → reads coderm.extensions.eagerActivation
  → ImplicitActivationEvents.setEagerExtensions(Set{...})

Extension host startup
  → _handleEagerExtensions() → _activateByEvent("*")
  → Listed extensions activate immediately (eager phase)

Test plan

• Install asvetliakov.vscode-neovim from the marketplace
• Launch Coderm and open a text file
• Verify neovim mode is active immediately without pressing any key
• Check coderm.extensions.eagerActivation appears in Settings UI
• Set the value to [] and restart — verify normal (lazy) activation behavior

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