Keep URI maintenance surface focused

[zchee]

Summary

This PR keeps the URI package maintenance surface focused after the strict
anti-slop cleanup pass.

It removes stale lint configuration copied from unrelated code paths, trims
redundant test scaffolding, and makes vector fixture failures report clearer
evidence. The only production-code change is a small internal POSIX path helper
modernization using Go 1.26-compatible standard-library APIs.

Changes

• Remove obsolete .golangci.yaml exclusions for files that are not part of
  this module.
• Delete a duplicate With test case that covered the same authority-clearing
  behavior twice.
• Make allocation gate expectations table-driven instead of switching on test
  case names.
• Use slices.Contains directly in vector metadata checks.
• Fail explicitly when vector fixtures contain an unknown error name.
• Modernize POSIX path helper internals with strings.SplitSeq and
  strings.Builder while preserving the existing URI path behavior.

Impact

• Reduces stale policy surface in lint configuration.
• Makes future test failures easier to diagnose.
• Avoids new dependencies and preserves public API behavior.
• Keeps the cleanup small and deletion-heavy: 5 files changed,
  21 insertions, 83 deletions.

Validation

• go test -count=1 ./...
• make test
• gopls check $(git ls-files '*.go' ':!:vendor/**')
• go vet ./...
• tools/bin/golangci-lint run ./...
• git diff --check
• govulncheck ./...

[codecov]

Codecov Report

❌ Patch coverage is 95.45455% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 88.4%. Comparing base (77008ac) to head (3b145b1).
⚠️ Report is 2 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
posixpath.go	95.4%	1 Missing ⚠️

@@          Coverage Diff          @@
##            main      #5   +/-   ##
=====================================
  Coverage   88.4%   88.4%           
=====================================
  Files         10      10           
  Lines        829     840   +11     
=====================================
+ Hits         733     743   +10     
- Misses        96      97    +1     

Flag	Coverage Δ
Linux-ARM64	88.4% <95.4%> (+<0.1%)	⬆️
Linux-X64	90.4% <95.0%> (-0.1%)	⬇️

Files with missing lines	Coverage Δ
posixpath.go	89.3% <95.4%> (+0.1%)	⬆️

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[zchee]

/gemini review

[gemini-code-assist]

Code Review

This pull request simplifies linter configurations in .golangci.yaml, refactors allocation tests in fspath_test.go to use a cleaner struct-driven approach, and optimizes path operations in posixpath.go by utilizing strings.SplitSeq and strings.Builder. Additionally, test helpers in vector_test.go are updated to use standard library functions and improve error reporting. Feedback is provided on posixpath.go to further optimize posixJoin by bypassing strings.Builder for single non-empty paths and pre-allocating the builder's capacity to minimize allocations.

[zchee]

/gemini review

[gemini-code-assist]

Code Review

This pull request cleans up and optimizes several components. In .golangci.yaml, unused linter overrides and comments are removed. In posixpath.go, path normalization and joining are optimized to reduce allocations by using strings.SplitSeq and strings.Builder with pre-allocated capacity. Test files are also refactored: fspath_test.go simplifies allocation gate testing with a table-driven approach, change_test.go removes a redundant test case, and vector_test.go leverages standard library functions (slices.Contains) and improves error handling in vector tests. There are no review comments, so no further feedback is provided.