docs: Update server SDK feature flag examples

[dustinbyrne]

Changes

• Builds on docs: Update Python documentation for evaluate_flags API #16684 and updates server SDK feature flag docs to use the new snapshot-style APIs as the canonical path:
  • Node evaluateFlags()
  • Go EvaluateFlags()
  • Ruby evaluate_flags() with enabled? / get_flag
  • PHP evaluateFlags()
  • .NET EvaluateFlagsAsync()
  • Elixir PostHog.FeatureFlags.evaluate_flags/2
  • Rust evaluate_flags()
  • Java server evaluateFlags()
• Updates shared feature flag snippets, local evaluation/property override examples, experiment examples, library pages, and related exposure/cost/stale flag guidance.
• Replaces old automatic capture flag-enrichment snippets (sendFeatureFlags, send_feature_flags, SendFeatureFlags, appendFeatureFlags) with passing evaluated snapshots to captures/events.
• Deletes unreferenced server-side group flag snippets and obsolete send-feature-flags snippets.

Validation: ran git diff --check.

Notes for review:

• Ruby's SDK snapshot method is enabled?() rather than is_enabled().
• Elixir attaches evaluated flags through process context with PostHog.FeatureFlags.set_in_context(snapshot) rather than a capture(flags: ...) argument.
• .NET OnlyAccessed() falls back to all flags if called before any access; the docs avoid the empty-snapshot warning language used by other SDKs.
• Existing tutorials still use older single-flag APIs in several places; I left them alone to keep this PR focused on SDK docs/reference pages.

Checklist

• I've read the docs and/or content style guides.
• Words are spelled using American English
• Use relative URLs for internal links
• I've checked the pages added or changed in the Vercel preview build
• If I moved a page, I added a redirect in vercel.json

[github-actions]

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Status	Details	Updated (UTC)
🔴 Failed	View logs	May 01, 2026 11:20PM

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Common culprits

• MDX issues - unescaped </> characters, unclosed tags, or malformed JSX
• External API timeouts - GitHub, Strapi, or Ashby occasionally hiccup

[github-actions]

Vale prose linter → found 7 errors, 225 warnings, 27 suggestions in your markdown

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File	Errors	Warnings	Suggestions
contents/docs/experiments/adding-experiment-code.mdx	0	4	0
contents/docs/experiments/exposures.mdx	1	13	0
contents/docs/experiments/installation/dotnet.mdx	0	2	1
contents/docs/experiments/installation/rust.mdx	0	1	1
contents/docs/experiments/legacy-methodology.mdx	0	11	0
contents/docs/experiments/troubleshooting.mdx	0	13	2
contents/docs/feature-flags/cleaning-up-stale-flags.mdx	0	9	0
contents/docs/feature-flags/cutting-costs.mdx	0	24	0
contents/docs/feature-flags/installation/rust.mdx	0	1	0
contents/docs/feature-flags/local-evaluation/index.mdx	4	8	0
contents/docs/feature-flags/property-overrides.mdx	0	3	2
contents/docs/feature-flags/snippets/flag-charge-estimate.mdx	0	2	0
contents/docs/feature-flags/user-and-group-targeting.mdx	0	0	3
contents/docs/integrate/feature-flags-code/_snippets/feature-flags-code-dotnet.mdx	0	5	2
contents/docs/integrate/feature-flags-code/_snippets/feature-flags-code-elixir.mdx	0	3	2
contents/docs/integrate/feature-flags-code/_snippets/feature-flags-code-go.mdx	0	4	2
contents/docs/integrate/feature-flags-code/_snippets/feature-flags-code-java.mdx	0	4	2
contents/docs/integrate/feature-flags-code/_snippets/feature-flags-code-node.mdx	0	4	2
contents/docs/integrate/feature-flags-code/_snippets/feature-flags-code-php.mdx	0	4	2
contents/docs/integrate/feature-flags-code/_snippets/feature-flags-code-ruby.mdx	0	4	2
contents/docs/integrate/feature-flags-code/_snippets/feature-flags-code-rust.mdx	0	4	2
contents/docs/libraries/dotnet/index.mdx	0	10	0
contents/docs/libraries/go/index.mdx	0	12	0
contents/docs/libraries/java/index.mdx	0	10	0
contents/docs/libraries/node/index.mdx	2	28	1
contents/docs/libraries/php/index.mdx	0	20	0
contents/docs/libraries/ruby/index.mdx	0	17	1
contents/docs/libraries/rust/index.mdx	0	5	0