chore: improve error management and documentation

[RonsenbergVI]

Pull Request

Type of change

• Bug fix
• New feature
• Refactor / internal cleanup
• Docs
• Other: chore

Description of the changes

• Improve error management (prevent errors being swallowed)
• Improve sentinel error documentation

Motivation for the changes

• Give more informational error messages

Breaking change?

• No
• Yes — details below

If yes, fill this in

What breaks:

Before → after:

// before

// after

Migration:

How it was tested

Checklist

• Tests pass locally
• Added/updated tests for the change (or explained why not)
• Docs updated if behavior changed

Notes for reviewers

[codecov]

Codecov Report

❌ Patch coverage is 51.85185% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 78%. Comparing base (e82eb02) to head (91d89a6).

Files with missing lines	Patch %	Lines
pkg/server/handlers.go	55%	8 Missing ⚠️
internal/cache/lru_cache.go	0%	3 Missing ⚠️
internal/config/config.go	0%	1 Missing ⚠️
internal/query/parser/parser.go	0%	1 Missing ⚠️

Additional details and impacted files

@@         Coverage Diff         @@
##           main    #54   +/-   ##
===================================
- Coverage    78%    78%   -1%     
===================================
  Files        39     39           
  Lines      2480   2492   +12     
===================================
+ Hits       1948   1954    +6     
- Misses      464    470    +6     
  Partials     68     68           

Files with missing lines	Coverage Δ
internal/containers/time.go	93% <100%> (ø)
internal/query/query.go	64% <100%> (ø)
pkg/db/db.go	65% <100%> (ø)
internal/config/config.go	39% <0%> (ø)
internal/query/parser/parser.go	62% <0%> (ø)
internal/cache/lru_cache.go	45% <0%> (ø)
pkg/server/handlers.go	70% <55%> (-6%)	⬇️

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