docs: administration: monitoring: document filter drop_bytes metric

[eschabell]

Add the missing fluentbit_filter_drop_bytes_total row to the v2 metrics
table. The counter is registered in src/flb_filter.c but was absent from
the documented filter metrics.

Signed-off-by: Eric D. Schabell eric@schabell.org

Summary by CodeRabbit

• Documentation
  • Documented the fluentbit_filter_drop_bytes_total metric, which reports the number of log-record bytes dropped by filters and removed from the data pipeline.

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ℹ️ Recent review info

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Configuration used: defaults

Review profile: CHILL

Plan: Team

Run ID: b956fb0e-efb3-4395-9b49-af23d0891362

📥 Commits

Reviewing files that changed from the base of the PR and between 9d072fd and dfeec84.

📒 Files selected for processing (1)

• administration/monitoring.md

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📝 Walkthrough

Walkthrough

Changes

Monitoring metrics

Layer / File(s)	Summary
Document filter drop bytes metric administration/monitoring.md	Adds the fluentbit_filter_drop_bytes_total counter to the v2 metrics table. The entry describes dropped log-record bytes and the filter instance name label.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Merge Risk: ⚪ Minimal · up to dfeec

This change only documents an existing filter-drop-bytes metric and does not alter runtime behavior. No actionable merge-blocking risk remains after normal checks and review.

Suggested reviewers: guangxuecao

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the documentation change for the filter drop-bytes metric.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
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.

Full details: Docstring Coverage

Explanation

No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0 files. (1 skipped: 1 unsupported.)

✨ Finishing Touches

🧪 Generate unit tests (beta)

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[eschabell]

@patrick-stephens ready for review!