fix: env2bool matches truthy values exactly

[aryansk]

Fixes #11080.

What

dvc.utils.env2bool decided truthiness with an unanchored re.search("1|y|yes|true", ...), so any env value that merely contained 1, y, yes or true was treated as true — e.g. my_path, anything, only, v1.0, yep.

Why

env2bool is used for DVC_EXP_AUTO_PUSH, DVC_IGNORE_ISATTY, DVC_SQLALCHEMY_ECHO and DVC_TEST, so unrelated values silently flip behavior on. The truthy values were always intended to be exactly 1 / y / yes / true.

How

Match the exact truthy values (case-insensitively) instead of a substring search:

return var.lower() in {"1", "y", "yes", "true"}

Tests

Parametrized regression test covering the intended truthy/falsy values plus the false positives above; all fail on main, pass with the fix. tests/unit/utils and the env2bool-adjacent suites (test_progress, test_analytics, test_updater) pass; ruff check + format clean.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.98%. Comparing base (2431ec6) to head (ff1732e).
⚠️ Report is 213 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11081      +/-   ##
==========================================
+ Coverage   90.68%   90.98%   +0.30%     
==========================================
  Files         504      505       +1     
  Lines       39795    41146    +1351     
  Branches     3141     3263     +122     
==========================================
+ Hits        36087    37436    +1349     
- Misses       3042     3071      +29     
+ Partials      666      639      -27     

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