docs: add fern docs for 26.04 PRs (#1160, #1575, #1576, #1603, #1612, #1652)

[lbliii]

Description

Add fern documentation and release notes for features merged to main but not yet documented on 26.04-staging. Covers audio preprocessing stages (MonoConversion, SegmentConcatenation, TimestampMapper from PR #1575), audio band filtering (BandFilterStage from PR #1576), Nemotron VLM video captioning support (PR #1160), fuzzy dedup LSH memory tuning params (PR #1603), interleaved IO schema improvements (PR #1652), and dependency/security updates (PR #1612). Includes new pages, updated existing pages, nav updates, and release note line items with breaking changes.

Checklist

• I am familiar with the Contributing Guide.
• New or Existing tests cover these changes.
• The documentation is up to date with these changes.

[greptile-apps]

Greptile Summary

This documentation-only PR backfills Fern docs and release notes for six features that were merged to main but not yet documented on the 26.04-staging branch. It adds two new MDX pages (audio preprocessing overview and band filtering), updates the video captioning page to cover Nemotron VLM alongside Qwen-VL, adds LSH GPU memory-tuning parameters to the fuzzy deduplication page, updates the navigation config, and adds corresponding release-note entries including security CVE references and breaking changes.

Key changes:

• New fern/versions/v26.04/pages/curate-audio/process-data/preprocessing/ section covering MonoConversionStage, SegmentConcatenationStage, and TimestampMapperStage
• New band-filtering.mdx documenting BandFilterStage with CPU/GPU and local-model usage
• captions-preview.mdx updated with a Nemotron VLM tab, variant table, and updated parameter descriptions — two prose sentences in the "Preparation" and "Caption generation" sections still reference Qwen-specific output keys and model names and were not updated alongside the new content
• fuzzy.mdx extended with lsh_num_output_partitions, lsh_rmm_pool_size, and lsh_spill_memory_limit parameter docs
• Release notes correctly cover all six PRs, including breaking changes (WebdatasetReaderStage rename, source_id_field removal, LSH default changes) and security dependency bumps

Confidence Score: 4/5

Safe to merge; documentation-only changes with no runtime risk, minor stale prose in captions-preview.mdx.

All changes are MDX documentation files and a YAML navigation config — no executable code is modified. The two stale Qwen-specific references in captions-preview.mdx are minor inaccuracies that won't break anything but could confuse Nemotron VLM users. Everything else is accurate and well-structured.

fern/versions/v26.04/pages/curate-video/process-data/captions-preview.mdx — two prose sections still mention Qwen-specific output keys after Nemotron VLM support was added.

Important Files Changed

Filename	Overview
fern/versions/v26.04/pages/curate-video/process-data/captions-preview.mdx	Nemotron VLM support added, but two prose sections in "Preparation and previews" and "Caption generation and enhancement" still reference Qwen-specific output keys and model name, creating stale documentation.
fern/versions/v26.04/pages/curate-audio/process-data/preprocessing/index.mdx	New audio preprocessing overview page; TimestampMapperStage is imported from nemo_curator.stages.audio.postprocessing while MonoConversionStage/SegmentConcatenationStage come from preprocessing — worth verifying against actual module locations.
fern/versions/v26.04/pages/about/release-notes/index.mdx	Well-structured release notes covering six PRs; security CVE references, breaking changes (rename, removed parameter, default changes), and new features are clearly documented.
fern/versions/v26.04/pages/curate-text/process-data/deduplication/fuzzy.mdx	Clean addition of three new LSH memory-tuning parameters with good explanation and a concrete 40GB GPU example; existing content untouched.
fern/versions/v26.04/pages/curate-audio/process-data/preprocessing/band-filtering.mdx	New band filtering documentation; comprehensive coverage of configuration, GPU usage, local model usage, and pipeline example with clear parameter tables.
fern/versions/v26.04.yml	Navigation config correctly adds the new Preprocessing section with Overview and Band Filtering pages under curate-audio.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Raw Audio Files] --> B[MonoConversionStage\nConvert to mono, verify sample rate]
    B -->|strict_sample_rate=True| C{Sample rate\nmatch?}
    C -->|No| D[Filtered out]
    C -->|Yes| E[VADSegmentationStage\nnested=True]
    E --> F[SegmentConcatenationStage\nAssemble waveform, insert silence between segments]
    F --> G[Downstream Processing\nASR, Quality Assessment, BandFilterStage, etc.]
    G --> H[TimestampMapperStage\nResolve segment positions to original timestamps]
    H --> I[Metadata Output\noriginal_file, original_start_ms, original_end_ms]

    style D fill:#f88,stroke:#c00
    style I fill:#8f8,stroke:#090

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Comments Outside Diff (2)

1. fern/versions/v26.04/pages/curate-video/process-data/captions-preview.mdx, line 122 (link)

   Stale Qwen-only reference in preparation step description

   This prose description still says "formats model‑ready inputs for Qwen‑VL" even though CaptionPreparationStage now supports both "qwen" and "nemotron" variants. A reader following the Nemotron VLM tab above would find this description contradictory.

2. fern/versions/v26.04/pages/curate-video/process-data/captions-preview.mdx, line 208 (link)

   Hardcoded Qwen output-key references are now stale

   This sentence hard-codes Qwen-specific internal output keys (window.caption["qwen"] and window.enhanced_caption["qwen_lm"]). Since CaptionEnhancementStage now also accepts model_variant="nemotron" (as shown in the parameters table added in this PR), a reader using the Nemotron path will find these key names confusing or incorrect. Consider generalising the description to be model-agnostic, similar to how step 1 was updated:

_{Reviews (1): Last reviewed commit: "docs: add fern docs for 26.04 PRs (#1575..." | Re-trigger Greptile}