find: name the program as invoked in every message

[sylvestre]

Use the base name of argv[0] instead of a hardcoded find:, matching the report added next, minus the .exe that Windows adds. Unchanged when invoked as find.

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[codecov]

Codecov Report

❌ Patch coverage is 77.77778% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.22%. Comparing base (015dc1f) to head (bcb7dcb).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/find/mod.rs	60.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #876      +/-   ##
==========================================
- Coverage   92.27%   92.22%   -0.06%     
==========================================
  Files          35       35              
  Lines        7499     7524      +25     
  Branches      390      390              
==========================================
+ Hits         6920     6939      +19     
- Misses        437      443       +6     
  Partials      142      142              

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[codspeed]

Merging this PR will not alter performance

✅ 20 untouched benchmarks

---

_{Comparing sylvestre:find-program-name (bcb7dcb) with main (526221e)}

[github-actions]

Commit bcb7dcb has test result changes:

bfs testsuite:

Test results comparison:
  Current:   TOTAL: 316 / PASSED: 273 / FAILED: 37 / SKIPPED: 6
  Reference: TOTAL: 317 / PASSED: 274 / FAILED: 37 / SKIPPED: 6

Changes from main branch:
  TOTAL: -1
  PASSED: -1
  FAILED: +0

No result in this run (1) - hung, crashed, or renamed:
  ? posix/depth_error (was PASS)