feat(node): Add build-time opt-out for runtime channel injection

[mydea]

Stacked on #23473.

Adds a build-time opt-out for the Node SDK's runtime diagnostics-channel injection, complementing the runtime enableRuntimeChannelInjection option from the base PR.

• New __SENTRY_CHANNEL_INJECTION__ treeshaking flag, mirroring __SENTRY_TRACING__: when a bundler text-replaces it with false, the registerDiagnosticsChannelInjection() / detectOrchestrionSetup() block in init is dropped, and its transitive orchestrion-register code tree-shakes away.
• Exposed through the bundler plugins' bundleSizeOptimizations.excludeChannelInjection, which maps to __SENTRY_CHANNEL_INJECTION__ = false via the same mechanism as excludeTracing.
• The gate now reads both the build flag and the runtime option: (typeof __SENTRY_CHANNEL_INJECTION__ === 'undefined' || __SENTRY_CHANNEL_INJECTION__) && options.enableRuntimeChannelInjection !== false.

🤖 Generated with Claude Code

[github-actions]

size-limit report 📦

⚠️ Warning: Base artifact is not the latest one, because the latest workflow run is not done yet. This may lead to incorrect results. Try to re-run all tests to get up to date results.

Path	Size	% Change	Change
@sentry/browser	30.3 kB	-	-
@sentry/browser - with treeshaking flags	28.47 kB	-	-
@sentry/browser - with treeshaking flags tracing without tracing	26.81 kB	-	-
@sentry/browser (incl. Tracing)	48.62 kB	-	-
@sentry/browser (incl. Tracing + Span Streaming)	48.64 kB	-	-
@sentry/browser (incl. Tracing, Profiling)	51.51 kB	-	-
@sentry/browser (incl. Tracing, Replay)	88.02 kB	-	-
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	77.42 kB	-	-
@sentry/browser (incl. Tracing, Replay with Canvas)	92.74 kB	-	-
@sentry/browser (incl. Tracing, Replay, Feedback)	105.45 kB	-	-
@sentry/browser (incl. Feedback)	47.65 kB	-	-
@sentry/browser (incl. sendFeedback)	35.13 kB	-	-
@sentry/browser (incl. FeedbackAsync)	40.28 kB	-	-
@sentry/browser (incl. Metrics)	31.24 kB	-	-
@sentry/browser (incl. Logs)	31.52 kB	-	-
@sentry/browser (incl. Metrics & Logs)	32.15 kB	-	-
@sentry/react	32.09 kB	-	-
@sentry/react (incl. Tracing)	50.81 kB	-	-
@sentry/vue	35.34 kB	-	-
@sentry/vue (incl. Tracing)	50.61 kB	-	-
@sentry/svelte	30.33 kB	-	-
CDN Bundle	31.61 kB	-	-
CDN Bundle (incl. Tracing)	48.96 kB	-	-
CDN Bundle (incl. Logs, Metrics)	33.8 kB	-	-
CDN Bundle (incl. Tracing, Logs, Metrics)	50.87 kB	-	-
CDN Bundle (incl. Replay, Logs, Metrics)	74.31 kB	-	-
CDN Bundle (incl. Tracing, Replay)	86.53 kB	-	-
CDN Bundle (incl. Tracing, Replay, Logs, Metrics)	88.37 kB	-	-
CDN Bundle (incl. Tracing, Replay, Feedback)	92.24 kB	-	-
CDN Bundle (incl. Tracing, Replay, Feedback, Logs, Metrics)	94.18 kB	-	-
CDN Bundle - uncompressed	93.84 kB	-	-
CDN Bundle (incl. Tracing) - uncompressed	146.82 kB	-	-
CDN Bundle (incl. Logs, Metrics) - uncompressed	100.14 kB	-	-
CDN Bundle (incl. Tracing, Logs, Metrics) - uncompressed	152.51 kB	-	-
CDN Bundle (incl. Replay, Logs, Metrics) - uncompressed	229.08 kB	-	-
CDN Bundle (incl. Tracing, Replay) - uncompressed	266.08 kB	-	-
CDN Bundle (incl. Tracing, Replay, Logs, Metrics) - uncompressed	271.76 kB	-	-
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed	279.78 kB	-	-
CDN Bundle (incl. Tracing, Replay, Feedback, Logs, Metrics) - uncompressed	285.45 kB	-	-
@sentry/nextjs (client)	53.36 kB	-	-
@sentry/sveltekit (client)	49.04 kB	-	-
@sentry/core/server	65.56 kB	-	-
@sentry/core/browser	51.78 kB	-	-
@sentry/node	117.49 kB	+0.04%	+44 B 🔺
@sentry/node/import (ESM hook with diagnostics-channel injection)	85.18 kB	-	-
@sentry/node - without tracing	87.49 kB	+6.71%	+5.5 kB 🔺
@sentry/aws-serverless	95.84 kB	+4.84%	+4.42 kB 🔺
@sentry/cloudflare (withSentry) - minified	194.61 kB	-	-
@sentry/cloudflare (withSentry)	481.16 kB	-	-

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