DEV: add TCEs to XADD command page

[dwdougherty]

Note

Low Risk
Low risk documentation/sample-only change, but it adds many new multi-language example files that could fail doc-sample compilation/tests if formatting or client APIs are off.

Overview
Updates content/commands/xadd.md to use clients-example blocks for XADD, covering both basic stream appends and Redis 8.6+ idempotent production via IDMP/IDMPAUTO (plus XCFGSET configuration).

Adds a new cmds_stream example set under local_examples/ (Go, Node, Python, Java/Jedis, Java/Lettuce async+reactive, Rust async+sync, and .NET) implementing the xadd1 and xadd2 steps with assertions/cleanup to support docs-driven testing.

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[github-actions]

DOC-5640

[github-actions]

Staging links:
https://redis.io/docs/staging/DOC-5640/commands/xadd/

[jit-ci]

🛡️ Jit Security Scan Results

✅ No security findings were detected in this PR

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^{Security scan by Jit}

[mich-elle-luna]

one question, otherwise seems fine though I can't review for techincal

[dwdougherty]

Thank you for the review and spotting the error, @mich-elle-luna!