feat(gradle): Start implementing Gradle filter module with task-type detection

[Nava2]

Overview

This PR series adds a Rust-native Gradle filter module that replaces the existing src/filters/gradle.toml TOML filter (~60% savings) with 85-99% token savings through task-type detection, stack trace intelligence, and batch processing.

Tested on Faire's production Gradle monorepo. Upstreamed from Faire's fork where it has been in use since January 2026.

Value over existing gradle.toml

The upstream TOML filter does basic noise stripping. This Rust module adds:

• Task-type detection (compile, test, detekt, health, proto, deps) with per-type filtering strategies
• Stack trace intelligence — keeps user frames + first assertion frame, drops framework noise (configurable via drop_frame_packages)
• Batch processing — splits multi-task output by > Task boundaries, applies per-section filters
• Path normalization — converts absolute paths to repo-relative
• Configurable — user_packages, extra_drop_patterns, drop_frame_packages via config.toml or .rtk.toml

Token Savings

Filter	Savings	Strategy
Global noise	70-90%	RegexSet (37 patterns), Try-block removal, ANSI stripping
Compile	85%+	Drop kapt/KSP noise, normalize paths (RegexSet)
Test	90%+	Drop passing tests, truncate stack traces
Detekt	85%+	Group violations by rule (RegexSet)
Health	80%	Passthrough (already concise after global)
Proto	75%+	Drop extraction noise
Deps	40%+	Truncate dependency tree to depth 0-1
Batch	95%+	Per-task routing on multi-task runs

Staging PRs (internal review)

Each filter is a separate PR for focused review in Faire/rtk:

#	PR	Scope	Savings
3a	#23	GradleConfig struct	—
3b-i	#33	Global noise filters + path normalization + insta dep	70-90%
3b-ii	#34	Command routing + task-type detection	—
3c	#35	Compile filter	85%+
3d	#36	Test filter	90%+
3e	#37	Detekt filter	85%+
3f	#38	Health filter	80%
3g	#39	Proto filter	75%+
3h	#40	Deps filter	40%+
3i	#41	Batch processing	95%+
3j	#42	Discover rule + retire TOML	—

Performance

• All noise pattern matching uses RegexSet for single-pass matching (global: 37 patterns, compile: 4, detekt: 3)
• Zero async — single-threaded, no tokio
• All regexes compiled once via lazy_static!

Open Questions

1. New dev-dependency: insta 1.46 for snapshot testing. Is this acceptable? Dev-only (not in release binary). Used for 16 snapshot files validating filter output format.

Size

~2,800 lines code + 13 fixtures + 16 snapshots (across 10 Rust files)

🤖 Generated with Claude Code

[Nava2]

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