feat(01-learn): add 18-input-output-guardrails tutorial

[SyedAn-Git]

Adds Input/Output Guardrails tutorial to python/01-learn/

Covers:

• Input guardrails (BeforeInvocationEvent)
• Output guardrails (AfterInvocationEvent) with BLOCK/REDACT
• Custom content filters (regex, keyword, format compliance)
• GuardrailPlugin (HookProvider pattern)
• Tool call validation (BeforeToolCallEvent)
• Error handling (fail-open vs fail-closed)

Tested on SageMaker Studio with strands-agents 1.40.0

[SyedAn-Git]

@manoj-selvakumar5 Ready for review. This is the Input/Output Guardrails tutorial.

[SyedAn-Git]

Pushed a fix commit (476e346) — inlined content filter classes directly into notebooks and added logger definitions so each notebook runs independently without cross-file dependencies. All 6 notebooks tested clean on SageMaker Studio.

[manoj-selvakumar5]

Hi @SyedAn-Git - There's some overlap with 01-learn/16-hooks-lifecycle and 03-integrate/guardrails/ so I'd suggest moving this to 05-technical-use-cases/guardrails/ treating hooks as a prerequisite instead of re-teaching them.

[SyedAn-Git]

Thanks for the review, @manoj-selvakumar5! I've addressed the overlap feedback:

Moved the tutorial from 01-learn/18-input-output-guardrails/ → 05-technical-use-cases/guardrails/custom-python-guardrails/ (via git mv, so history is preserved).

Reframed hooks as a prerequisite instead of re-teaching them:

1. Added an explicit Prerequisites section in the README pointing to 01-learn/16-hooks-lifecycle for the hook mechanics (HookProvider, register_hooks, writable event fields).
2. Updated the notebook intro cells to reference 16-hooks-lifecycle and stopped re-explaining the hook lifecycle, each step now applies hooks to guardrails rather than teaching them.

Clarified how this relates to the other guardrail samples, the README now distinguishes the three approaches: this pure-Python/hooks sample, the managed 01-learn/05-guardrails (Amazon Bedrock Guardrails), and the third-party 03-integrate/guardrails integrations.

Re-tested: all 6 notebooks execute end-to-end with zero cell errors on strands-agents 1.53.0. The guardrail-specific code cells are unchanged from the original.