Oversized fields overflow to media; sessionId filter added

What's Changed

Features

• feat(mcp): Add canonical MCP tool outcome telemetry to DD by @LysanderKie in https://github.com/langfuse/langfuse/pull/15620
• feat(ingestion): move oversized direct-event fields to media by @hassiebp in https://github.com/langfuse/langfuse/pull/15350
• feat(ingestion): trace observation field overflow by @hassiebp in https://github.com/langfuse/langfuse/pull/15649
• feat(ingestion): measure overflow processing duration by @hassiebp in https://github.com/langfuse/langfuse/pull/15654
• feat(mcp): expose metrics query discovery metadata by @LysanderKie in https://github.com/langfuse/langfuse/pull/15621
• feat(mcp): expose observation scope requirements by @LysanderKie in https://github.com/langfuse/langfuse/pull/15624
• feat(preview): expose v4 migration UI flag by @maxdeichmann in https://github.com/langfuse/langfuse/pull/15651

Fixes

• fix(worker): skip token counts instead of synchronous tokenization fallback by @Steffen911 in https://github.com/langfuse/langfuse/pull/15627
• fix(ci): cut ci-runtime-analyst cost and raise its credit ceiling by @wochinge in https://github.com/langfuse/langfuse/pull/15639
• fix(ci): ignore zizmor ref-version-mismatch for gh-aw compiled workflow by @Steffen911 in https://github.com/langfuse/langfuse/pull/15644
• fix(ui): present oversized fields as attachments by @hassiebp in https://github.com/langfuse/langfuse/pull/15648
• fix(web): update oversized media attachment test by @wochinge in https://github.com/langfuse/langfuse/pull/15650
• perf(worker): skip tokenization when cost details are provided by @Steffen911 in https://github.com/langfuse/langfuse/pull/15638
• fix(mcp): enrich dashboard widget validation errors by @LysanderKie in https://github.com/langfuse/langfuse/pull/15630
• fix: Add sessionId filtering to v2 observations API by @sumerman in https://github.com/langfuse/langfuse/pull/15646
• fix(mcp): accept reversed metrics order aliases by @LysanderKie in https://github.com/langfuse/langfuse/pull/15623
• fix(mcp): coerce exact tags metrics filters by @LysanderKie in https://github.com/langfuse/langfuse/pull/15622
• fix(mcp): accept exact observation id filters by @LysanderKie in https://github.com/langfuse/langfuse/pull/15625

Chores

• ci(deps): bump the github-actions group across 1 directory with 16 updates by @dependabot[bot] in https://github.com/langfuse/langfuse/pull/15643
• chore(agent-dx): scope agent guidance to packages and validate it in CI by @wochinge in https://github.com/langfuse/langfuse/pull/15653

Full Changelog: https://github.com/langfuse/langfuse/compare/v4.1.0...v4.2.0