fix(enforcement): strengthen test-with-code rule -- new source files must include tests

[MScottAdams]

Problem

The existing testing gate in main.md (t1.6.1) says "no implementation is complete until tests are written and task check passes." Agents interpret this as "run existing tests and confirm they pass" rather than "write new tests for new code." The v0.17.0 swarm (#233) shipped 5 new Python scripts with zero unit tests because task check passed on the existing suite.

Proposal

Strengthen the test-with-code requirement across 4 surfaces:

1. AGENTS.md -- hard gate (always-loaded)

Add ! rule to "Before committing" section:

• ! New source files (scripts/, src/, cmd/, *.py, *.go) MUST include corresponding test files in the same PR. Running existing tests is not sufficient -- new code requires new tests.

2. main.md -- strengthen existing testing gate

Update the Decision Making testing gate (t1.6.1) to explicitly distinguish:

• "tests pass" = existing tests still pass (regression)
• "tests written" = new code has new test coverage (forward)

3. deft-swarm prompt template -- CONSTRAINT line

Add to the CONSTRAINTS section of the prompt template:

• New source files must have corresponding tests -- do not push a PR with untested new code

4. deft-build SKILL.md -- pre-commit checklist

Add explicit check: "For each new source file in this PR, verify a corresponding test file exists"

Future (deterministic enforcement, #233 scope)

A task verify:test-coverage that diffs new .py/.go files against new test_.py/_test.go files and fails if new code has no corresponding tests. This replaces the prompt-driven rule with a binary pass/fail gate.

[MScottAdams]

Roadmap Refresh Analysis (2026-04-10)

Category: Enforcement gap / behavioral rule strengthening

Summary: The existing testing gate (t1.6.1) is interpreted as "run existing tests" rather than "write new tests for new code." The v0.17.0 swarm shipped 5 new Python scripts with zero unit tests because task check passed on the existing suite. Proposes explicit "new code = new tests" rules across 4 surfaces: AGENTS.md (! rule in Before committing), main.md (distinguish regression vs. forward coverage), deft-swarm prompt template (CONSTRAINT line), deft-build checklist (per-new-file verification step).

Relationship to existing issues:

• t1.6.1 (testing enforcement gate, completed v0.10.1) -- this strengthens that rule
• test: add unit tests for v0.17.0 deterministic task scripts #293 (unit tests for v0.17.0 scripts) -- direct consequence of this gap
• More Determinism #233 (More Determinism, Phase 5) -- future task verify:test-coverage deterministic gate noted as out-of-scope here

Scope: Small -- 4 targeted text additions across AGENTS.md, main.md, deft-swarm SKILL.md, and deft-build SKILL.md. No new files.

Recommendation: Phase 1 Cleanup -- same class as t1.6.1 (enforcement hardening); caused the #293 gap and will recur in the next swarm without an explicit rule.