feat(processor,ui): migrate LUFS target to -16 and add LUFS value to filenames

[flexiondotorg]

Summary

Migrate the loudness normalisation target from -18 to -16 LUFS and enhance output filenames to include the final measured LUFS value. These changes align the codebase with expert guidance on podcast loudness standards and provide users with immediate visibility of achieved loudness.

Changes

LUFS Target Migration (-18 → -16)

• Update NormTargetLUFS constant and all defaults in internal/processor/filters.go
• Replace hardcoded LUFS target values with constant references in internal/processor/adaptive.go and internal/logging/recording_tips.go
• Update gain calculations and comments across processor and logging packages

Output Filename Enhancement

• Implement post-processing rename to include measured LUFS: <name>-LUFS-NN-processed.<ext>
• NN is final integrated loudness rounded to nearest integer (e.g., -15.8 LUFS → LUFS-16)
• Fix OutputPath propagation in TUI model for correct filename display on completion
• Update test cleanup to handle both old and new filename patterns

User-Facing Updates

• Display input filename during active processing (output filename unknown until completion)
• Update all documentation (README, AGENTS.md, technical docs) to reflect -16 LUFS target
• Clarify EBU R128 distinction in comparison documentation (-23 LUFS standard vs -16 LUFS podcast target)

Testing

• All existing tests pass (just test)
• Full grep audit confirms no stale LUFS target references remain
• Verified all remaining "-18" references are correctly LA-2A thresholds (dB RMS), test inputs, or unrelated metrics
• Build successful with clean compilation

Related Issues

Implements expert guidance on podcast loudness standards.

[cubic-dev-ai]

3 issues found across 15 files

Confidence score: 4/5

• This PR looks safe to merge with minimal risk: all reported issues are low-severity documentation/comment accuracy problems rather than runtime behavior regressions.
• The most significant issue is in README.md, where calling -16 LUFS a podcast/broadcast standard is factually incorrect and could mislead users about loudness targets.
• internal/processor/normalise.go and docs/Levelator-Comparison-And-Gap-Analysis.md contain wording/stage-label mismatches that can confuse maintenance and expectations, but they do not indicate functional breakage.
• Pay close attention to README.md, internal/processor/normalise.go, and docs/Levelator-Comparison-And-Gap-Analysis.md - align LUFS terminology and processing-stage descriptions to avoid reader confusion.

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="internal/processor/normalise.go">

<violation number="1" location="internal/processor/normalise.go:116">
P3: This parameter comment names the wrong file stage: normalisation reads the intermediate `-processed` output, and the `-LUFS-NN-processed` rename happens afterward.</violation>
</file>

<file name="README.md">

<violation number="1" location="README.md:9">
P2: `-16 LUFS` is a podcast target, not the broadcast standard; calling it the "podcast/broadcast standard" is factually inaccurate.</violation>
</file>

<file name="docs/Levelator-Comparison-And-Gap-Analysis.md">

<violation number="1" location="docs/Levelator-Comparison-And-Gap-Analysis.md:77">
P3: This sentence now misstates the target as `broadcast-ready`: the same document later correctly says EBU R128 broadcast loudness is -23 LUFS, while Jivetalking targets -16 LUFS for podcasts.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[cubic-dev-ai]

0 issues found across 1 file (changes from recent commits).

_{Requires human review: Auto-approval blocked by 2 unresolved issues from previous reviews.}

[cubic-dev-ai]

0 issues found across 2 files (changes from recent commits).

_{Requires human review: This PR modifies core processing targets (-18 to -16 LUFS) and changes the output filename convention, which are significant functional changes requiring human review.}