fix(signer): respect allow_all_sighashes in SignerWrapper::sign_input

[muhahahmad68]

Description

SignOptions::allow_all_sighashes is documented as controlling whether the signer will accept non-SIGHASH_ALL sighash types. However, the check only existed inside Wallet::sign as a PSBT-wide pre-flight guard. The underlying SignerWrapper<PrivateKey>::sign_input never consulted it, meaning callers using InputSigner or TransactionSigner directly could bypass the check entirely.

Added a sighash guard in SignerWrapper<PrivateKey>::sign_input before the match self.ctx dispatch. This ensures the check covers all signing contexts (Legacy, Segwitv0, Taproot) and all delegating implementations in a single place.

Tests Added

• Taproot input with SIGHASH_NONE and allow_all_sighashes: false returns NonStandardSighash
• Same setup with allow_all_sighashes: true passes the guard successfully

Fixes #469

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran just p before pushing

New Features:

• N/A

Bugfixes:

• This pull request breaks the existing API
• I've added tests to reproduce the issue which are now passing
• I'm linking the issue being fixed by this PR

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 80.07%. Comparing base (a9ad3b9) to head (8c6d411).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
src/wallet/signer.rs	88.88%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #476      +/-   ##
==========================================
+ Coverage   80.05%   80.07%   +0.01%     
==========================================
  Files          24       24              
  Lines        5360     5369       +9     
  Branches      244      249       +5     
==========================================
+ Hits         4291     4299       +8     
  Misses        990      990              
- Partials       79       80       +1     

Flag	Coverage Δ
rust	80.07% <88.88%> (+0.01%)	⬆️

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[benthecarman]

instead of these assert_ne!s it'd be more readable if you're asserting if it is Ok(())

here and below

[benthecarman]

after you've had one successful sig, it'll always succeed because it is already signed. you also need to clear out the signatures before each. Imo would be cleanest to start with base_psbt and for each assertion clone it and make modifications as you need, that way you don't have any risk of secondary effects

[muhahahmad68]

Makes more sense, I'll effect the changes as suggested. Much thanks @benthecarman