Backfill coverage gaps and exclude non-product files from coverage

[gabrieldeespindula]

Supersedes #288, rebuilt on top of current master (post-octocov, #289). The content is @pnzrfst's work, cherry-picked as a single clean commit with his authorship — the original branch carried the couve commits from #285/#286, which were closed in favor of #289.

What it does

• Removes width_box from nfce_lib/header.rb — dead code since Shrink licensee name to fit #159 (2021), never called.
• Adds specs for the method_missing/respond_to_missing? delegation in the three Document classes (cce_lib, danfe_lib/nfe_lib, danfe_lib/nfce_lib). Each was mutation-tested manually in Backfill coverage gaps closed by the gate #288.
• Excludes non-product files from coverage: /lib/prawn/ (Prawn internals monkey-patch, from Backfill coverage gaps closed by the gate #288) and /spec/support/ (rescued from Fail the PR when its changed files aren't fully covered #286, orphaned when it was closed).

Result

Line coverage goes from 99.5% to 100.0% (3595/3595) — verified locally with the full suite green.

The octocov comment on this PR is also the first real demonstration of the delta against the master baseline recorded since #289 landed.

🤖 Generated with Claude Code

[github-actions]

Code Metrics Report

	master (1c84fe4)	#290 (f3cdb31)	+/-
Coverage	99.5%	100.0%	+0.4%
Test Execution Time	21s	19s	-2s

Details

  |                     | master (1c84fe4) | #290 (f3cdb31) |  +/-  |
  |---------------------|------------------|----------------|-------|
+ | Coverage            |            99.5% |         100.0% | +0.4% |
  |   Files             |              114 |            111 |    -3 |
  |   Lines             |             3616 |           3595 |   -21 |
- |   Covered           |             3598 |           3595 |    -3 |
+ | Test Execution Time |              21s |            19s |   -2s |

Code coverage of files in pull request scope (94.7% → 100.0%)

Files	Coverage	+/-	Status
lib/br_danfe/cce_lib/document.rb	100.0%	+8.0%	affected
lib/br_danfe/danfe_lib/nfce_lib/document.rb	100.0%	+12.5%	affected
lib/br_danfe/danfe_lib/nfce_lib/header.rb	100.0%	+2.0%	modified
lib/br_danfe/danfe_lib/nfe_lib/document.rb	100.0%	+2.7%	affected
lib/prawn/font.rb	0.0%	-100.0%	affected
lib/prawn/font_metric_cache.rb	0.0%	-93.4%	affected
spec/br_danfe/cce_lib/document_spec.rb	100.0%	0.0%	modified
spec/br_danfe/danfe_lib/nfce_lib/document_spec.rb	100.0%	0.0%	modified
spec/br_danfe/danfe_lib/nfe_lib/document_spec.rb	100.0%	0.0%	modified
spec/support/have_same_content_of.rb	0.0%	-44.5%	affected

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Reported by octocov