docs: Launch campaign assets and V2 DSL documentation - #24

Summary

• Add launch campaign assets and recording packages.
• Update runtime demos and promoted examples to use V2 DSL syntax.
• Make public DSL documentation V2-only and remove the stale V1 guarantees page.
• Add a custom StreamForge documentation color scheme for Just the Docs.

Validation

• cargo test
• cargo fmt --check
• git diff --check
• cargo run --quiet --bin streamforge-validate -- examples/production/user-filtering.yaml
• cargo run --quiet --bin streamforge-validate -- examples/production/multi-tenant-filtering.yaml
• cargo run --quiet --bin streamforge-validate -- examples/production/cross-region-replication.yaml
• cargo run --quiet --bin streamforge-validate -- examples/aggregation/orders-windowed-metrics.yaml
• cargo run --quiet --bin streamforge-validate -- examples/aggregation/orders-quantiles.yaml
• V2-only grep check for the updated public docs and promoted examples

Notes

• Local docs build was not run because the repository does not include a Gemfile for a bundled Jekyll setup.
• The local .gitignore, .agents/, and AGENTS.md changes are not part of this PR.