feat(api): update API spec from langfuse/langfuse 1999706 (#1615)

* feat(api): update API spec from langfuse/langfuse 1999706

* feat(scores): add TEXT type to score overloads and docstrings

Extend string-value overloads in create_score, score_current_span,
score_current_trace, score, and score_trace to accept TEXT alongside
CATEGORICAL. Update all related docstrings. Add ExperimentScoreType
to exclude TEXT from experiments/evals. Add integration test for TEXT
scores.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* docs: simplify openapi spec update instructions in CONTRIBUTING.md

The spec update is now automated via PR from the langfuse repo.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(scores): update stale casts and export ExperimentScoreType

Update cast(Literal["CATEGORICAL"], ...) to include "TEXT" in
score/score_trace/score_current_span/score_current_trace impl bodies.
Add ExperimentScoreType to __all__ in types.py.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* ci: fix tests by adding dynamic retry

* tests: adapt to update server logic

* ci: cache pnpm store instead of node_modules to avoid stale server state

Caching node_modules directly caused postinstall hooks (e.g. prisma
generate) to be skipped, leading to stale generated artifacts that
didn't match the current langfuse-server schema. Cache the pnpm store
instead so installs are still fast but hooks run properly.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* ci: revert caching changes

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Co-authored-by: langfuse-bot <langfuse-bot@langfuse.com>
Co-authored-by: Tobias Wochinger <tobias.wochinger@clickhouse.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>