fix(mutmut): dotted-load doc_claim_scan/sources/structural + repo_badge_catalog for real mutation coverage (#292)

[cdeust]

Summary

scripts/check_doc_claims.py bare-imports its siblings doc_claim_scan,
doc_claim_sources, doc_claim_structural; scripts/generate_repo_badges.py
bare-imports repo_badge_catalog. A function's __module__ is fixed at
definition time to whatever name it was imported under
(mutmut/mutation/trampoline.py, module != decorated_func.__module__), so
every mutant in these bare-imported siblings reported "no tests" under a
scoped mutmut run, even though the functions ARE exercised by real passing
tests through the bare-imported path. Same defect class as
badge_render.py/doc_claim_structural.check_badge_floor (issues #262,
#280, #293).

Note on scope (updated after a concurrent-main conflict): doc_claim_sources.py's
instance of this exact defect was independently fixed by PR #304 (issue
#235), which merged to main while this PR was in flight. This PR's scope
is now the two remaining siblings — doc_claim_scan.py and
doc_claim_structural.py's remaining functions — plus repo_badge_catalog.py.
Rebased onto main past #304 and removed this PR's now-duplicate
doc_claim_sources dotted-load + direct-test class in favor of #304's
CanonicalSourceDirectTests (verified equivalent coverage before deleting
the duplicate — see "Real tally" below).

Fix

• Dotted-load each remaining sibling module under its own "scripts.<name>"
importlib.util.spec_from_file_location spec (mirroring the existing
  check_badge_floor/doc_claim_sources precedent already in
  tests_py/scripts/test_check_doc_claims.py).
• Add direct test classes (DocClaimScanDirectTests, StructuralDirectTests
  in test_check_doc_claims.py; RepoBadgeCatalogDirectTests in
  test_generate_repo_badges.py) that call through these dotted references
  instead of through gate's/gen's bare-imported copies, so mutmut's
  trampoline activates and attributes the mutant to a real test.
• Every assertion is exact (assertEqual on the full message string or the
  full dict), not assertIn — a partial match leaves string-literal and
  dict-key mutants unpinned. Added targeted continue-vs-break tests
  (multi-file scans where an earlier missing/skipped file must not cut the
  loop short) for the loop-shaped mutants exact string matching alone
  doesn't reach.
• One genuine pre-existing gap found and fixed en route (boy-scout, not a
  mutation-attribution artifact): check_scanned_json_parses's
  FileNotFoundError branch (a missing scanned .json file) had no test at
  all before this change, direct or indirect.
• CHANGELOG entry added (boy-scout, found on re-verification): every
  prior fix in this exact defect family (Mutation testing cannot attribute mutants for any scripts/ module (synthetic module names in tests_py/scripts) #262/fix(mutmut): dot the last scripts/ test-loader gap, make pip_constraint_sets.py mutation-testable (#262) #280's badge_render/
  check_badge_floor, check_doc_claims.py: 25 surviving mutants in the canonical-source helpers #235's doc_claim_sources, and Any two PRs that add tests conflict on six files by construction (test count hard-coded) #293 itself) carries
  an [Unreleased] ### Fixed entry; this fix's own commit had shipped
  without one. Added, matching the established convention and content.

No production code changed — this is test-only, restoring correct mutation
attribution for functions that were already correct and already tested
(save the one genuine gap above).

Real tally, not the absence of an error

Rebased onto current main (1bef0f5, past #304's doc_claim_sources fix)
and re-run from scratch rather than trusting stale numbers. A scoped
mutmut run (scripts/mutation_check.sh) against all four production
files (including doc_claim_sources.py, to confirm #304's fix and this
PR's fix compose cleanly with no regression) and both test files, on the
rebased tree:

>>> mutating: scripts/doc_claim_structural.py scripts/doc_claim_scan.py scripts/doc_claim_sources.py scripts/repo_badge_catalog.py | tests: tests_py/scripts/test_check_doc_claims.py tests_py/scripts/test_generate_repo_badges.py
    done (4 files mutated, 572 ignored, 0 unmodified)
97.21 mutations/second
🎉 301  🫥 0  ⏰ 0  🤔 0  🙁 0  🔇 0  🧙 0
>>> mutmut-reported survivors (must be empty, or documented equivalents):
  none — 0 surviving mutants 🎉

301 mutants generated, 301 killed, 0 reported "no tests" (🫥) — the
literal symptom #292 reports — and 0 survived (🙁), across all four
production files together (this PR's two remaining siblings plus #304's
already-merged doc_claim_sources fix). Before any dotted-load fix existed,
the equivalent scoped run against this PR's scope reported genuine
survivors once the "no tests" misattribution was fixed alone — confirming
both halves of the issue: the attribution defect was real, AND the
underlying functions needed additional test assertions to reach 0
survivors.

Completion Ledger

Path introduced	Asserting test
doc_claim_scan dotted-load + DocClaimScanDirectTests (14 tests)	tests_py/scripts/test_check_doc_claims.py::DocClaimScanDirectTests
doc_claim_structural remaining functions + StructuralDirectTests (17 tests, incl. 3 continue-vs-break tests + the new missing-json-file test)	tests_py/scripts/test_check_doc_claims.py::StructuralDirectTests
repo_badge_catalog dotted-load + RepoBadgeCatalogDirectTests (5 tests, exact-dict per badge)	tests_py/scripts/test_generate_repo_badges.py::RepoBadgeCatalogDirectTests
CHANGELOG [Unreleased] ### Fixed entry for this fix	reviewable directly in the diff; matches the established per-issue convention (#262/#280/#235/#293)

doc_claim_sources.py's dotted-load + CanonicalSourceDirectTests are
not in this PR's diff — they already merged via PR #304 (issue #235);
this PR's own duplicate of that class was removed during the rebase after
confirming #304's tests cover the same 4 functions with equivalent
(exact-message) assertions.

Rules compliance (coding-standards.md)

Rule	Status
§4.1 file size (300/500)	N/A — test files; repo convention already has test files well over 300/500 lines (test_launcher_deps.py 1500, benchmark_harness.py 1641); no production file touched
§4.2 method size (40 lines)	pass — measured by AST on the rebased tree; no function over 40 lines
§7 local reasoning	pass — no refused constructs; importlib.util.spec_from_file_location dotted-load mirrors the existing, reviewed precedent
§8 sourced constants	N/A — no new constants introduced
§12 mutation testing	pass — 0 surviving mutants, 0 "no tests" on the scoped 4-file run above, re-measured on the rebased tree (quoted, not asserted)
§14 boy-scout	pass — fixed the one genuine pre-existing test gap found en route (check_scanned_json_parses's missing-file branch) AND the missing CHANGELOG entry found on re-verification; removed this PR's own now-duplicate test class after #304 landed rather than leaving redundant coverage; no bypass used

Gates run (quoted, on the rebased head)

• pytest -q (full suite): 6938 passed, 5 skipped, 121 subtests passed in 184.25s (0:03:04)
• pytest --collect-only -q: 6943 tests collected
• python scripts/check_doc_claims.py --test-count 6943: doc claims OK (1 declared not-a-claim exemption(s))
• python scripts/generate_repo_badges.py --check --test-count 6943: badges OK (5 checked)
• ruff check . / ruff format --check .: All checks passed! / all files already formatted
• .bestpractices.json parses; no unresolved conflict markers anywhere (verified: only false-positive hits were RST table-divider === lines and a docstring ==== divider, neither a labelled <<<<<<</>>>>>>> marker)
• Targeted tests: tests_py/scripts/test_check_doc_claims.py tests_py/scripts/test_generate_repo_badges.py -q: 156 passed, 34 subtests passed

Closes #292