fix(observability): preserve browser and flush guarantees

[kojiwakayama]

Description

Follow-up to #3237 that closes late durability and cross-runtime compatibility gaps without adding third-party dependencies.

• Serialize file-log durability syncs with the write queue so a later flush() waits for writes accepted during an active flush.
• Capture immutable node:util/types brand checks synchronously at the runtime trust boundary while keeping browser and edge module graphs free of Node builtin imports.
• Fail closed on supported server runtimes when complete native brand checks are unavailable instead of silently weakening validation.
• Centralize the minimum Node.js contract for the root and first-party npm packages, reject extension engine overrides below that floor, and align public runtime documentation.
• Preserve synchronous Node, Deno, Bun, browser, and edge behavior without top-level-await or dynamic-import lifecycle hangs.
• Add focused regressions for flush interleaving, browser-safe exports, hostile globals, runtime compatibility, npm metadata, and documentation consistency.

Runtime support after this change:

• Node.js 22.3 or later
• Deno 2.2 or later
• Bun 1.1 or later

Review context:

• fix(observability): harden telemetry boundaries #3237 (comment)
• fix(observability): harden telemetry boundaries #3237 (comment)

Related Issue(s)

Follow-up to #3237.

Type of Change

• Bug fix
• New feature
• Breaking change: raises the documented and published minimum Node.js and Deno versions
• Documentation update
• Code refactoring
• Performance improvement
• Test update

Checklist

• Public runtime requirements and API guidance match the implementation
• Focused regression tests cover the corrected behavior
• Core remains free of third-party runtime dependencies
• Browser and edge public exports remain linkable

Verification

• Full integration suite: 256 tests / 2,595 steps passed
• Full observability suite: 52 files / 871 steps passed
• Focused compatibility, telemetry, and file-log tests passed
• Browser-safe export tests passed
• npm build and Node 22 install smoke passed
• Deno 2.2 and Bun 1.1 runtime checks passed
• deno task verify:quick
• git diff --check

[kojiwakayama]

@codex review

[Copilot]

Pull request overview

This PR is a follow-up observability fix that keeps the public observability surface browser-linkable while tightening FileLogSubscriber.flush() durability guarantees so later flushes wait for writes accepted during an active flush.

Changes:

• Make src/platform/compat/error-introspection.ts load node:util/types only on detected Node-compatible hosts (via dynamic import) to preserve browser/edge linkability.
• Serialize file-log durability syncs with the write queue so a later flush() does not resolve while writes accepted during an active flush are still pending.
• Add targeted regressions: flush interleaving coverage in file-log-subscriber.test.ts and expand browser-safe export checks.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/platform/compat/error-introspection.ts	Replaces static node:util/types import with conditional dynamic import to keep browser imports linkable.
src/observability/file-log-subscriber.ts	Refactors flush tracking to snapshot the queue and gate new writes behind a flush barrier.
src/observability/file-log-subscriber.test.ts	Adds a regression test for flush interleaving (writes queued during an active flush).
scripts/build/browser-safe-exports.test.ts	Updates/extends browser bundle assertions for the observability public barrel.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 27 out of 27 changed files in this pull request and generated no new comments.