chore: stdout for span exporter

[nikhilsinhaparseable]

if env OTEL_EXPORTER_OTLP_ENDPOINT or OTEL_EXPORTER_OTLP_TRACES_ENDPOINT set to stdout
export the traces to stdout

Summary by CodeRabbit

• New Features

  • Added support for exporting application traces to stdout in JSON format via the OTEL_EXPORTER_OTLP_ENDPOINT environment variable; environment-variable behavior and header handling for stdout are clarified.
  • Simplified tracing enablement so a single endpoint lookup determines whether tracing is active.

• Chores

  • Added a dependency to enable stdout-based OpenTelemetry export.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 2089e386-732b-479b-aea7-0042b6121f61

📥 Commits

Reviewing files that changed from the base of the PR and between ce280fd and 6e472d4.

📒 Files selected for processing (1)

• src/telemetry.rs

🚧 Files skipped from review as they are similar to previous changes (1)

• src/telemetry.rs

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Walkthrough

This PR adds opentelemetry-stdout and updates init_tracing to treat OTEL_EXPORTER_OTLP_ENDPOINT=stdout (case-insensitive) as a sentinel that builds a stdout JSON span exporter wrapped in a BatchSpanProcessor; non-stdout endpoints continue to build protocol-specific OTLP exporters inside the match with warnings/None on errors or unknown protocols.

Changes

OpenTelemetry Stdout Exporter Support

Layer / File(s)	Summary
Dependency and documentation Cargo.toml, src/telemetry.rs (lines 36–37)	Adds opentelemetry-stdout = "0.31.0" dependency and documents that OTEL_EXPORTER_OTLP_ENDPOINT=stdout writes spans as JSON to stdout, clarifying header behavior in that mode.
Stdout exporter routing in init_tracing src/telemetry.rs (lines 48–135)	Refactors endpoint resolution to check for stdout sentinel first and build a BatchSpanProcessor-wrapped stdout exporter; non-stdout endpoints trigger protocol-specific exporter construction inside the match, with logging on build failure and None return for unknown protocols.

🎯 3 (Moderate) | ⏱️ ~20 minutes

"I hopped into the tracer queue,
and painted spans in JSON blue,
stdout hums a merry tune,
while collectors wait in moonlit June,
a rabbit's trace, light and true." 🐇✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 inconclusive)

Check name	Status	Explanation	Resolution
Description check	❓ Inconclusive	The description is minimal but conveys the core intent. However, it lacks the structured format from the template and omits the testing/documentation checklist.	Consider using the repository's PR template structure with sections for Description, key changes, and the testing/documentation checklist to improve clarity and consistency.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: adding stdout as a span exporter option when OTEL environment variables are set to 'stdout'.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@src/telemetry.rs`:
- Around line 56-62: The current logic sets use_stdout by comparing only the
resolved endpoint string (variable endpoint) to "stdout", missing cases where
the traces-specific env var is "stdout"; update the logic to independently read
OTEL_EXPORTER_OTLP_ENDPOINT and OTEL_EXPORTER_OTLP_TRACES_ENDPOINT (using the
same env::var calls or constants used now), and set use_stdout = true if either
value exists and equals "stdout" (case-insensitive), while keeping the existing
endpoint resolution behavior for non-"stdout" values; adjust references to the
variables endpoint and use_stdout in telemetry setup accordingly.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 47bbef2e-9ab0-4da2-9ef5-6807bf0e853e

📥 Commits

Reviewing files that changed from the base of the PR and between 64928ab and ce280fd.

⛔ Files ignored due to path filters (1)

• Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (2)

• Cargo.toml
• src/telemetry.rs