[MEDIUM] Diagnostic squiggles may not be painted #38

The render_overlay handler on_render_diagnostic_squiggles has been replaced with a no-op, and the diagnostic spans are expected to be added to the buffer's _properties by lsp.store_diagnostics. However, the diff for lsp_client.lua (which defines store_diagnostics) is truncated, and the function is not shown to call buf:add_properties_span or similar. If store_diagnostics does not add the spans, diagnostic underlines will be missing. The old code added spans directly to the SpanManager via sm:add_properties_span.

• Files: src/cursed/editor_listeners.lua (lines 165-169 show empty function), src/cursed/lsp_client.lua (unseen store_diagnostics implementation)
• Commit: bd04fbe1 (refactor: move properties spans from SpanManager to Buffer)

Verify that lsp.store_diagnostics now writes to buf:add_properties_span or buf:set_properties. If not, diagnostic squiggles will not render.

Commit range: bd04fbe1

Related commits: bd04fbe1, 2a7cf991