fix(cli): wire --debug flag to logger level

[beep-boopp]

Description

The --debug flag is defined in the CLI but initLogger never reads it — the log level is hardcoded to slog.LevelInfo regardless. This means all Debug() calls across setup and instrument phases are silently filtered out.

This wires cmd.Bool("debug") to set slog.LevelDebug when the flag is active, Debug output goes to debug.log in the work directory, consistent with existing logging behavior.

Motivation

The flag has never actually worked, it was introduced in #50 as "-debug" (triple dash), #281 fixed the typo but the wiring to the logger was never added. There are 13 existing Debug() calls across the codebase that are currently unreachable.

Fixes #497

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Checklist

• PR title follows conventional commits format
• Code formatted: make format
• Linters pass: make lint
• Tests pass: make test
• Tests added for new functionality
• Tests follow testing guidelines
• Documentation updated (if applicable)

[codecov]

Codecov Report

❌ Patch coverage is 62.50000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 63.13%. Comparing base (08d86e9) to head (ba88777).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
tool/cmd/main.go	62.50%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #499      +/-   ##
==========================================
+ Coverage   62.83%   63.13%   +0.29%     
==========================================
  Files          62       62              
  Lines        4765     4771       +6     
==========================================
+ Hits         2994     3012      +18     
+ Misses       1527     1509      -18     
- Partials      244      250       +6     

Flag	Coverage Δ
tool	63.13% <62.50%> (+0.29%)	⬆️

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[beep-boopp]

Hey @y1yang0 just a heads up with the stderr tee, --debug surfaces a pretty verbose existing log in find.go:122 that dumps the full build plan as a single field. Makes the terminal output noisy. Should I drop the stderr tee and keep this to just the level fix, or is the tee worth keeping?

[y1yang0]

I prefer keeping it as the fix only

[beep-boopp]

I have added Sources: cli.EnvVars(...) and simplified the os.Getenv check. Integration test failure is a pre-existing timeout on Windows (same 600s timeout reproduces on main without my changes, tested that locally).

[Copilot]

Pull request overview

This PR wires the CLI --debug flag into logger level selection and adds an environment variable path so child toolexec invocations can inherit debug logging.

Changes:

• Adds OTELC_DEBUG as a shared environment variable constant.
• Sources the --debug flag from OTELC_DEBUG.
• Sets slog.LevelDebug and exports OTELC_DEBUG=1 when debug mode is enabled.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
tool/util/shared.go	Adds the shared OTELC_DEBUG environment variable constant.
tool/cmd/main.go	Reads the debug flag/env source and uses it to configure logger level and child process propagation.

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[beep-boopp]

Hey @y1yang0 all review feedback has been addressed, PTAL when you have the time thank you.

[y1yang0]

Please fix test failure

[beep-boopp]

Hey @y1yang0 so i added unit tests for initLogger covering default level, debug flag , env var propagation and cli.envVars sourcing. Remaining codecov gap is error return paths....that i cant trigger without mocking stdlib but atleast integration tests are passing now.

do let me know if any changes are to be made....