fix(filter-quality): preserve error signal in go test/vet/golangci filters

[aeppling]

Problem

These three Go filters all caused agent retries with the same root cause: RTK kept the cosmetic summary but dropped the one actionable line (the error/failure message), then advertised a verbose tee-log. So agents retried — cat/tail/grep-ing the firehose or re-running with --out-format overrides — pulling back more bytes than the unfiltered output.

Fixes (all in src/cmds/go/)

Filter	Before	After
go test	summary + [full output: …go_test.log] pointer to the raw go test -json dump (3–8× verbose); agents cat'd it on failure	drop the tee — build errors & per-test failures are already inline
go vet	only .go: lines kept → location-less fatal error: pcap.h: No such file or directory dropped, then "No issues found" on a hard failure; message truncated mid-line	keep every finding line; never claim success on failure; no mid-message truncation
golangci-lint	counts grouped by linter/file — the violation message (Text) was parsed and discarded	standard file:line:col: message (linter) findings, linter counts as a header
golangci-lint	force-parsed JSON even when the user passed --out-format, emitting golangci-lint (JSON parse failed: …) (reads as a tool failure)	passthrough verbatim on user --out-format/--output.* flags

Compression

Savings stay high vs raw — golangci 78–84% (was a misleading ~93% that omitted the message). go vet passes tiny failures through at ~0% by design: compressing 323 B costs a retry turn for no gain. go test compression slightly improved (pointer removed). The lost percentage points are repaid many times over by eliminating the 12–169 KB retry reads the missing signal caused.

Out of scope

Cross-cutting idempotency items (pipe-awareness, re-run escalation, full-path basename matching) live in the hook/rewrite + session-state layer, not these filters — left for a follow-up.

Testing

• cargo fmt --all · cargo clippy --all-targets (clean) · cargo test --all → 2073 passed, 0 failed, 7 ignored
• New tests: cgo build-failure surfaces inline (go test); location-less cgo error + no mid-message truncation (go vet); message+location surfaced + clean parse-failure passthrough + format-flag detection (golangci)