add: ignore DVC metadata matched by globs

[tandede]

Description

Repeated dvc add --glob calls currently fail because the second call also matches the .dvc stage files generated by the first one. Those metadata paths are passed to output validation and rejected as data outputs.

This change filters *.dvc, dvc.yaml, and dvc.lock only when they come from wildcard expansion. Explicit metadata targets keep the existing validation error, while repeated glob calls can update already tracked files and add new matches.

Fixes #11086.

Test plan

• pytest -q — 3051 passed, 11 skipped, 2 xpassed
• pytest -q tests/func/test_add.py — 68 passed, 1 skipped
• mypy dvc/repo/add.py
• pre-commit run --files dvc/repo/add.py tests/func/test_add.py
• Reproduced the CLI failure before the change and verified two consecutive dvc add --glob "data/*" calls succeed after it

• ❗ I have followed the Contributing to DVC checklist.

• 📖 This fix preserves the documented --glob behavior and does not require a documentation update.

Thank you for the contribution - we'll try to review it as soon as possible. 🙏

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

❌ Patch coverage is 92.85714% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.98%. Comparing base (2431ec6) to head (4feca1b).
⚠️ Report is 213 commits behind head on main.

Files with missing lines	Patch %	Lines
dvc/repo/add.py	85.71%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11087      +/-   ##
==========================================
+ Coverage   90.68%   90.98%   +0.30%     
==========================================
  Files         504      505       +1     
  Lines       39795    41163    +1368     
  Branches     3141     3268     +127     
==========================================
+ Hits        36087    37452    +1365     
- Misses       3042     3071      +29     
+ Partials      666      640      -26     

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