improve offline tx handling

[Fraccaman]

Describe your changes

Closes #3417.

Checklist before merging

• If this PR has some consensus breaking changes, I added the corresponding breaking:: labels
  • This will require 2 reviewers to approve the changes

[codecov]

Codecov Report

Attention: Patch coverage is 86.48649% with 20 lines in your changes missing coverage. Please review.

Project coverage is 72.68%. Comparing base (521511f) to head (34c6ac4).
Report is 13 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/core/src/key/common.rs	79.48%	8 Missing ⚠️
crates/core/src/hash.rs	84.84%	5 Missing ⚠️
crates/tx/src/lib.rs	91.37%	5 Missing ⚠️
crates/sdk/src/tx.rs	80.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3715      +/-   ##
==========================================
+ Coverage   72.49%   72.68%   +0.19%     
==========================================
  Files         338      338              
  Lines      104190   104309     +119     
==========================================
+ Hits        75535    75822     +287     
+ Misses      28655    28487     -168     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[sug0]

just a couple of suggestions

[sug0]

    integration::ledger_tests::pgf_governance_proposal

failed

[tzemanovic]

yeah, seeing this in #3718 and #3735 after rebase too

[dan-u410]

there's another (broken) offline signing cmd, namada client sign-tx might be nice to deprecate that in favor of sign-offline being developed here