test(kr-7): generator-index must be positive (no sigma 0, no negative index) (#25)

KR-7 from PROOF-NARRATIVE.md §3: `sigma N`, `sigma_inv N`, `cup N`,
`cap N` must be accepted iff N >= 1.

The canonical parser in `KRLAdapter.jl` raises a "zero index" error
for `sigma 0` etc., and negative indices are outside the lexer's
positive-Int recognition. The smoke test now asserts that no
committed example contains such a pattern.

Added check 4b in tests/smoke/grammar_smoke.sh:

  - Grep examples for `<gen> 0` — fail if present.
  - Grep examples for `<gen> -<digits>` — fail if present.
  - Report pass for examples with no violation.

This is a positive smoke check, not a parser-correctness proof; full
KR-7 discharge requires a parser-level property test (deferred to
follow-up — see PROOF-NEEDS.md TG-K3 entry). The smoke version
catches accidental commits of malformed examples and stays in the
existing lexical-level CI lane.

Verified locally:
  - Original 4 examples: 20 passing checks (was 16; added 1 KR-7
    pass per file × 4 files).
  - Synthetic example `let bad = (sigma 0); close bad;` correctly
    fails with "generator with zero index violates KR-7 (sigma 0)".

Cross-references:
- PROOF-NARRATIVE.md KR-7 (added in PR #23)
- ASSUMPTIONS.md A-KR-2.1
- TEST-NEEDS.md TG-K3 (added in PR #23)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

tests/smoke/grammar_smoke.sh

@@ -118,6 +118,26 @@ for file in "${EXAMPLE_FILES[@]}"; do
         fi
     done
 
+    # 4b. KR-7: generator indices must be POSITIVE (N >= 1).
+    # The canonical parser in KRLAdapter.jl raises a "zero index" error
+    # for `sigma 0`, `sigma_inv 0`, etc., and negative indices are
+    # outside the lexer's positive-Int recognition. The smoke test
+    # asserts that no committed example contains such a pattern.
+    #
+    # See PROOF-NARRATIVE.md KR-7 and ASSUMPTIONS.md A-KR-2.1.
+    # NB: grep returns 1 when nothing matches; under `set -e` we
+    # capture into a variable with `|| true` to avoid exiting.
+    zero_violations=$(grep -oE '\b(sigma|sigma_inv|cup|cap)\b[[:space:]]+0\b' <<< "$stripped" || true)
+    if [[ -n "$zero_violations" ]]; then
+        report_fail "$name: generator with zero index violates KR-7 ($zero_violations)"
+    else
+        report_pass "$name: no generator-with-zero-index (KR-7 ok)"
+    fi
+    neg_violations=$(grep -oE '\b(sigma|sigma_inv|cup|cap)\b[[:space:]]+-[0-9]+' <<< "$stripped" || true)
+    if [[ -n "$neg_violations" ]]; then
+        report_fail "$name: generator with negative index violates KR-7 ($neg_violations)"
+    fi
+
     # 5. File must mention at least one operation family
     found_family=""
     grep -qE '\bsigma\b|\bsigma_inv\b|\bcup\b|\bcap\b' <<< "$stripped" && found_family="${found_family} CONSTRUCT"