feat(cli): --output json and --output junit to stdout

[Chemaclass]

Problem

--output <format> accepts exactly one value: tap (bashunit test --help, parsed at src/main/test.sh:72). Every other machine-readable format is file-only (--report-json, --report-junit, --report-tap, --report-html).

That forces a temp file into any pipeline that wants to post-process results:

./bashunit tests/ --report-json /tmp/r.json >/dev/null && jq '.tests[]|select(.status=="failed")' /tmp/r.json

when it should be:

./bashunit tests/ --output json | jq '.tests[]|select(.status=="failed")'

The formats and the writers already exist; only the destination is hard-coded.

Proposal

Extend --output to text (default) | tap | json | junit.

• Non-text formats send the report to stdout and suppress the human-readable console rendering, exactly as --output tap does today.
• Diagnostics and errors go to stderr so the stdout stream stays parseable.
• An unknown value exits non-zero listing the valid ones (Unknown options are silently ignored: a typo'd flag runs a different suite and exits 0 #871 class of bug).
• --output json and --report-json f.json in the same run are allowed and both are produced.

Where to change

• src/main/test.sh:72 (--output parsing) and src/main/validate.sh:60 (value validation).
• src/main/run.sh:132-150 — the reporters currently take a file path; give them a stdout path, or write to /dev/stdout consistently.
• src/reports/json.sh, src/reports/junit.sh, src/reports/tap.sh.
• src/console/* — the suppression switch that tap already uses.

Acceptance criteria

• --output json emits a single JSON document on stdout, valid per jq .
• --output junit emits XML on stdout
• --output tap is byte-identical to today (no regression)
• --output text equals no flag
• No console decoration, progress or header leaks into stdout for the machine formats
• Errors and warnings still reach stderr
• Exit codes unchanged across all formats
• --output json --report-json f.json produces both
• Unknown value exits non-zero with the valid list
• Works under --parallel (regression guard for fix(reports): every report format is empty under --parallel #1004)
• Acceptance tests piping each format through a parser

Repo checklist (agent)

• TDD: RED → GREEN → REFACTOR. Write the failing test first.
• Bash 3.0+ only: no printf -v, no += append, no declare -A, no [[ ]], no ${var,,}, no &>>, no ${arr[-1]}. Expanding a possibly-empty array under set -u needs ${arr[@]+"${arr[@]}"}.
• A new CLI flag must be wired in all of these or a parity test fails:
  • parse in src/main/test.sh (report-style flags need export -n, see src/main/test.sh:188-196 for why)
  • validate the value in bashunit::main::validate_config_or_exit (src/main/validate.sh:60) — unvalidated input used to run the wrong thing and exit 0 (Unknown options are silently ignored: a typo'd flag runs a different suite and exits 0 #871, --jobs with a non-integer value hangs on Bash 3.x and is silently ignored on Bash 4.3+ #873)
  • default + env var in src/config/env.sh and a documented line in .env.example
  • --help text in the same block it belongs to
  • both completions/bashunit.bash and completions/_bashunit (anti-drift test feat(cli): bash and zsh completion scripts with an anti-drift test #778 fails otherwise)
• Gates: make sa, make lint, ./bashunit tests/, ./bashunit --parallel tests/. Never run shfmt -w.
• Docs: update docs/command-line.md. Editing docs/assertions.md invalidates the bashunit doc acceptance snapshot — regenerate it.
• CHANGELOG.md: add one line under ## Unreleased.
• Fixtures under tests/acceptance/fixtures/ must not end in *test.sh.
• One issue = one PR.

[Chemaclass]

Done in #1064 (merged).