[yapishu]

Adds python -m nockchain inspect/sign and the installed nockchain command, plus inspect_signing_bundle and sign_signing_bundle library functions. Users save a bundle from the remote MCP, review it locally, and sign with a hidden zprv prompt or an explicit local key file. Recovery phrases require an explicit derivation path. Signing requires interactive approval, creates a new file with mode 0600, and does not broadcast. The package retains no runtime dependencies.

Validation reconstructs the payment plan from complete inputs and checks canonical encoding, commitments, existing signatures, maturity, recipients, change and fees, including small remainders assigned to fees. Signature verification can allow missing signatures while preserving its default threshold check. Network and tip fields describe indexed context, not a chain proof.

Implements the signing contract in https://github.com/SWPSCO/nockchain-rpc-server/pull/139 and matches SWPSCO/nockchain-js#3. Sets the package version to 0.3.0; publication is separate.

Validation:

• Full suite: 31 tests pass; signing tests pass after the final schema-field checks.
• Ruff checks and formatting pass.
• Five Rust-generated fixtures produce identical signed bytes and transaction IDs.
• Wheel and source distribution build and pass Twine validation.
• Installed wheel CLI passes inspection, refusal without approval, hidden-key signing, mode 0600 and overwrite-refusal checks.
• CI checks both installed entrypoints on Python 3.11 and 3.13.