[codex] Enable Kotlin LSP fixture coverage

[caydyan]

Fixes #123

Summary

• Enables Kotlin when USE_LSP=true selects the default LSP-backed fixture path.
• Keeps non-LSP Kotlin fixture assertions working while allowing mode-specific annotations with node_lsp / node_no_lsp, edge_lsp / edge_no_lsp, and absent_lsp / absent_no_lsp.
• Adds testing::test_kotlin so Kotlin runs through both graph backends in normal CI and through the Kotlin language server in LSP CI.
• Adds Kotlin LSP-only assertions for extra call edges that tree-sitter alone does not capture:
  • PersonList -> PersonViewModel.updatePerson
  • HomeViewModel.fetchUsers -> UserRepository.getUsers
• Avoids spawning an empty analyzer command when USE_LSP=true is used with a language that does not have an LSP executable configured.

BTC payout address: bc1qev5ant33v5y89qqjvcf4mh9hlax5svqf5xd7gc

Validation

• git diff --check
• cargo test -p lsp language::tests:: -- --nocapture --test-threads=1
• cargo test -p ast testing::test_kotlin -- --nocapture --test-threads=1
• PATH=/tmp/stakgraph-kls/server/bin:$PATH USE_LSP=true cargo test -p ast testing::test_kotlin -- --nocapture --test-threads=1
• cargo test -p ast --lib -- --test-threads=1
• PATH=/tmp/stakgraph-kls/server/bin:$PATH USE_LSP=true cargo test -p ast --lib -- --test-threads=1

Docker note

The current upstream base lsp/Dockerfile already installs kotlin-language-server and exposes the kotlin-language-server executable. This PR completes the remaining #123 wiring by enabling Kotlin in the USE_LSP=true path and adding mode-specific Kotlin fixture assertions that prove LSP captures extra cross-file call edges while the non-LSP path remains covered.

[caydyan]

Hosted checks are green on 109b0361 now:

• Run CLI integration tests
• Run e2e standalone tests
• Run e2e tests
• Run standalone tests
• Run unit tests
• Run unit tests with LSP

The follow-up fix scopes fixture node-count checks to files inside the fixture tree, so hosted Kotlin LSP external definitions no longer perturb the fixture assertions. PR is non-draft, mergeable, and CLEAN from the GitHub merge-state view.

Local validation also covered git diff --check, the Kotlin fixture in non-LSP and LSP modes, cargo test -p ast --lib -- --test-threads=1, and the LSP language tests.

[caydyan]

Quick follow-up after the 2026-06-14 submission: this is still ready for review.

Current GitHub checks are all passing on head 109b0361, the PR is non-draft and mergeable, and issue #123 has the bounty claim plus BTC payout address recorded. Happy to make any maintainer-preferred adjustments if the Kotlin LSP fixture expectations differ from this approach.