feat(testing): bootstrap 8 rule blocks in go-testing-guide

[bborbe]

Summary

Bootstraps `docs/go-testing-guide.md` — converts its 8 MUST sections into canonical `### RULE` blocks. Mirrors PRs #2-5, #8 template.

`rules/index.json`: 27 → 42 entries (8 new `go-testing/` + 7 `agent-cmd/*` that were forgotten in PR #9's commit).

Rules added

id	level	enforcement
`go-testing/no-stdlib-table-tests`	MUST	judgment
`go-testing/no-testing-t-direct`	MUST	judgment
`go-testing/no-bare-error-call`	MUST	judgment
`go-testing/suite-test-file-required`	MUST	judgment (file-existence)
`go-testing/main-test-with-compiles`	MUST	judgment (file-existence + body)
`go-testing/suite-timeout-required`	MUST	judgment
`go-testing/counterfeiter-mocks-required`	MUST	judgment
`go-testing/libtime-injection-required`	MUST	judgment (cross-refs `go-time/no-time-now-direct`)

All are mechanically enforceable in principle — ast-grep YAMLs deferred to focused follow-up PRs rather than blocking this bootstrap (same approach as PR #8 / `go-prometheus/counter-total-suffix`).

PR #9 cleanup

PR #9 trimmed the agent-cmd-guide and added 7 `agent-cmd/*` rule blocks but didn't include the `rules/index.json` walker output regen. Local `make build-index` here picked them up; included in this PR's diff. Net new for this PR specifically: 8 go-testing rules.

Pre-emptive checks (lessons from #6 + #8)

• `grep -nEi "personal/|/users/bborbe|~/documents/obsidian"` → clean
• Trading-term grep (`candle|epic|broker|signalstore`) → clean
• No internal contradictions (e.g. Good examples don't violate sibling rules)
• All cross-references (rule id ↔ index anchor ↔ rule YAML path) resolve

Test plan

• `make precommit` clean
• `make build-index` ran; index regenerated
• All 8 go-testing rules present with MUST level + owner `go-test-quality-assistant`
• 7 `agent-cmd/*` entries from PR docs: trim agent-command-development-guide to rules-only (1750 → 347 lines) #9 now indexed
• Bot review (via github-pr-watch)

[ben-s-pull-request-reviewer]

{
"verdict": "approve",
"summary": "The PR bootstraps 8 RULE blocks in docs/go-testing-guide.md and adds matching entries to rules/index.json. All four concerns from the plan were investigated: (1) the 7 agent-cmd/* entries are not duplicates — they were omitted from index.json during the PR #9 trim and are added here retroactively; (2) the cross-rule reference `go-time/no-time-now-direct` exists in index.json; (3) the new RULE blocks are structurally sound as documentation with enforcement marked as judgment/ast-grep follow-up; (4) the new entries are intentionally placed at the top of the array (agent-cmd before go-*, go-testing before go-time), consistent with logical grouping. No critical issues found.",
"comments": [
{
"file": "rules/index.json",
"line": 1,
"severity": "nit",
"message": "Should Fix: PR title says 'bootstrap 8 rule blocks in go-testing-guide' but this PR also adds 7 agent-cmd/* entries to rules/index.json (corresponding to the 7 RULE blocks added in the PR #9 trim of agent-command-development-guide.md). These agent-cmd entries were omitted from index.json in PR #9 and are added here retroactively. Consider splitting into separate commits or clarifying the title to mention both."
},
{
"file": "docs/go-testing-guide.md",
"line": 47,
"severity": "nit",
"message": "Nice to Have: All 8 new RULE blocks have enforcement marked as 'judgment (ast-grep follow-up)'. The rules are well-structured as documentation but mechanical enforcement via ast-grep YAML has not been implemented yet. This is expected for a bootstrap pass but should be tracked as follow-up work."
}
],
"concerns_addressed": [
"correctness: rules/index.json 7 agent-cmd/* entries — verified NOT duplicates from PR #9; PR #9 only touched docs/agent-command-development-guide.md, these index.json entries were never added and are correctly added now",
"correctness: go-testing/libtime-injection-required cross-rule reference 'go-time/no-time-now-direct' — verified exists in rules/index.json at line 367",
"correctness: 8 new RULE blocks reference 'ast-grep follow-up' — confirmed, rules are documentation-quality, enforcement not yet implemented (expected for bootstrap)",
"correctness: new entries inserted at top of JSON array — intentional; agent-cmd/* entries go before go-context/* (alphabetically first by domain), go-testing/* entries go before go-time/* (consistent with prior go-testing position)"
]
}