Add lsp stub services

[ssmifi]

WIP

Closes #28

Mostly ports from langium with go-idiomatic mechanisms for customization.

#	Feature	Pattern	Provider auto-registered?	Notes
1	Declaration	Provider-only	✅ Yes	Meaningful default (delegates to Definition)
2	Implementation	Filter	✅ Yes	Meaningful filter default (include-all)
3	Type Definition	Provider-only	✅ Yes	Meaningful default (cross-reference heuristic)
4	Semantic Tokens	Contributor (separate service)	✅ Yes	⚠️ No default contributor, provider does real work
5	Inlay Hint	Computer (constructor-injected)	✅ Yes	⚠️ No default computer, provider does real work
6	Signature Help	Computer (constructor-injected)	✅ Yes	⚠️ No default computer, provider does real work
7	Call Hierarchy	Interface-only	❌ No	--
8	Type Hierarchy	Interface-only	❌ No	--
9	Code Actions	Interface-only	❌ No	--
10	Code Lens	Interface-only	❌ No	--
11	Document Links	Interface-only	❌ No	--
12	Commands	Interface-only	❌ No	--

Tests the defaults and the override mechanisms.

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.50.

Benchmark suite	Current: 8be8f2b	Previous: d803417	Ratio
BenchmarkWorkspaceCycle (typefox.dev/fastbelt/examples/statemachine) - MB/s	13.82 MB/s	5.21 MB/s	2.65

This comment was automatically generated by workflow using github-action-benchmark.