Make capability registration resilient to unresponsive clients

[yasmewad]

Some LSP clients (such as Kiro CLI) don't respond to client/registerCapability or client/unregisterCapability
requests, which blocks lsp4j's message loop and hangs the server. This is especially problematic
because the unregister→register chain runs on every file change, workspace folder change, and
build file save (since clients don't de-duplicate file watchers).

Per the LSP 3.17 spec, dynamic registration is optional — "Not all clients need to support
dynamic capability registration" — and didChangeWatchedFiles has no static fallback
("the current protocol doesn't support static configuration for file changes from the server
side"). The server must degrade gracefully when registration isn't available.

Changes

• Best-effort capability registration: Added registerBestEffort() and
  unregisterBestEffort() helper methods that wrap all 6 registerCapability/
  unregisterCapability call sites with .exceptionally() handlers. Each call site
  logs a distinct warning describing which registration failed.

• Fixed unregister→register chains: Changed thenRun to thenCompose in the 3
  places that chain unregister then register (didChangeWatchedFiles,
  didChangeWorkspaceFolders, didSave). thenRun silently skips the re-registration
  if the upstream future completes exceptionally; thenCompose properly composes the
  two async operations so re-registration always proceeds.

• Removed unused version.properties: The createProperties Gradle task and startup
  banner in connect() were dead code. Removed along with their now-unused imports.

• Made StubClient extensible: Removed final modifier to allow test-specific
  subclasses that simulate client failures.

Testing

• initializedHandlesRegisterCapabilityFailure — verifies the server continues when
  registerCapability returns a failed future during startup
• unregisterFailureDoesNotBlockReRegistration — verifies the unregister→register
  chain in didChangeWatchedFiles still works when unregisterCapability fails
• After using the binary generated, it works well with agentic coding tools like Kiro CLI

[yasmewad]

Closing as I realized the existing binary pattern works with Kiro CLI. It was just that I was missing some setup instructions in correct order.