Add AllowBatchPublish stream config field

[mtmk]

Adds the AllowBatchPublish field on StreamConfig (JSON allow_batched), required by streams that opt in to fast ingest batch publishing per ADR-50. Matches the field added in nats.go (#2052) and nats.js (#379). Server-side support requires nats-server v2.14.0+. The fast-ingest publisher itself will live in orbit.net alongside the existing atomic batch publisher.

[synadia-claude-reviewer]

Claude finished @mtmk's task in 1m 55s —— View job

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PR Review: Add AllowBatchPublish stream config field

• Gather context (PR diff, CLAUDE.md, existing code)
• Review changed files for correctness, security, and API compatibility
• Post inline comments if needed
• Final summary

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Review Summary

The change is minimal and well-structured. No correctness, security, or performance issues found.

StreamConfig.cs — The new property follows the exact same pattern as AllowAtomicPublish:

• Correct JSON name allow_batched (per ADR-50)
• bool (non-nullable) with JsonIgnore(WhenWritingDefault) — serializes only when true, which is the correct wire behavior for opt-in flags
• XML doc includes the server version requirement

ManageStreamTest.cs — The test mirrors AllowAtomicPublish_property_should_be_set_on_stream faithfully:

• [SkipIfNatsServer(versionEarlierThan: "2.14")] correctly extends FactAttribute (no separate [Fact] needed)
• Version string "2.14" parses correctly via System.Version and will run on 2.14.0+
• The test exercises create → get → update(false) → get round-trip, which is the right pattern for a reversible flag (unlike AllowMsgSchedules which is one-way)

One minor observation: the AllowAtomicPublish test includes step-explaining comments but the new test omits them. Not a correctness issue.

LGTM.

[github-actions]

🚀 Deployed on https://69f33f9921a5951553bfba31--teal-klepon-7e92d0.netlify.app

[MauriceVanVeen]

LGTM