feat(zeph-tools): add declarative TOML-based output filter engine

[bug-ops]

Summary

• Add hybrid declarative TOML-based output filter engine with 9 strategy types
• Migrate all 6 hardcoded filters (cargo_build, test_output, clippy, git, dir_listing, log_dedup) into the declarative engine as named built-in strategies
• Expand default-filters.toml from 10 to 19 rules covering cargo, git, docker, npm, pip, make, pytest, go, terraform, kubectl, brew, ls, journalctl
• Simplify FilterConfig by removing 6 per-filter config structs (breaking change, pre-1.0)
• Delete 6 obsolete filter modules, gate CommandMatcher::Custom to tests only
• Security hardening: RegexBuilder size_limit, pattern cap, HashMap pre-allocation, NormalizeEntry validation

Test plan

• cargo +nightly fmt --check
• cargo clippy --workspace -- -D warnings (0 warnings)
• cargo nextest run --workspace --lib --bins (2284 passed)
• Unit tests for all 9 strategies (success, fallback, edge cases)
• Snapshot tests (cargo build, clippy, git status/diff, test summary)
• Proptest fuzz (strip_noise, truncate, test_summary, dedup)
• Integration tests (registry, custom TOML override, disabled rules)
• Compile-time validation tests (regex limits, empty patterns, file size)
• Compound command matching tests