fix: resolve mapped jsr with path correctly

[hasundue]

• chore(cli): add --debug option
• chore: better error message for unresolved import
• test: add a failing case (mapped jsr with path)

[codecov]

Codecov Report

Attention: Patch coverage is 68.42105% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 84.79%. Comparing base (d254e48) to head (f8c300c).

Files	Patch %	Lines
core/update.ts	0.00%	5 Missing ⚠️
core/dependency.ts	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #145      +/-   ##
==========================================
- Coverage   85.30%   84.79%   -0.51%     
==========================================
  Files          10       10              
  Lines        1184     1197      +13     
  Branches      209      212       +3     
==========================================
+ Hits         1010     1015       +5     
- Misses        172      180       +8     
  Partials        2        2              

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