feat: complete Sparkctl CLI command surface

[ProfRandom92]

Summary

Completes the local Sparkctl CLI command surface and synchronizes the project documentation.

CLI command surface

All known CLI placeholders are now wired and documented:

• agy-ct package compress
• agy-ct package adversarial
• agy-ct report export
• agy-ct notebook bundle
• existing schema/context/package commands remain aligned

Implemented backend modules

• report_export::run for Markdown report export from JSON reports
• notebook_bundle::run for nbformat v4 .ipynb bundle export from context JSON and optional render text

Documentation sync

• Updated README.md in German with current command status, matrix, Mermaid pipeline, integrity explanation, and non-claims boundaries.
• Updated docs/SPARK_ALIGNMENT.md with the final wired command list and test status.
• Preserved useful .antigravity/ and docs/context/ assets from the earlier Antigravity config branch without reintroducing obsolete README drift.

Validation

Local validation reported:

• cargo fmt --all --check passed
• cargo check --tests passed
• targeted report export integration test passed
• targeted notebook bundle integration test passed
• documentation now records 73 PASS tests

Safety / claim hygiene

• No production, legal, forensic, EU AI Act, or official SPARK/BMDS compliance claims introduced.
• Synthetic-only / human-review / non-certified boundaries preserved.
• No secrets, provider keys, production credentials, or remote service configuration added.

PR hygiene notes

• Supersedes the README-drift portion of PR docs: add Antigravity config and fix README drift #8.
• Preserves the useful .antigravity/ and docs/context/ assets from PR docs: add Antigravity config and fix README drift #8.
• Leaves PR docs: prepare Hugging Face paper materials #2 (paper-hf-prep) untouched because it is orthogonal Paper/Hugging Face draft material.

[gemini-code-assist]

Code Review

This pull request fully wires up the agy-ct CLI subcommands (including package compression, verification, replay, adversarial checks, and notebook bundling), implements structured error mapping (EVIDENCE_LOSS, CONSTRAINT_DRIFT) with ledger validation, separates replay output streams, and adds extensive integration tests and documentation for the SPARK Hackathon. The reviewer feedback is highly constructive and identifies critical path-handling bugs (such as empty parent paths when outputting to plain filenames), potential race conditions in temporary file generation, and a violation of the project's robust error handling standards due to an unsafe .unwrap() call.

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