docs: fix heading levels

[Planeshifter]

Description

Cross-package drift analysis of @stdlib/constants/float64 identified two high-confidence mechanical corrections. Both files have an H5 (#####) heading for the constant-identifier sub-section inside ## Usage where 65 of 67 sibling packages (97% conformance) and both float32 siblings use H4 (####).

Namespace summary

• Members analyzed: 67 non-autogenerated packages.
• Features analyzed: file tree, package.json shape (top keys, scripts, keywords), manifest.json shape, README section structure and heading levels, README <section class="…"> wrappers, README usage-block variable vs lib/index.js MAIN variable name, test/example file naming, module- and main-docblock JSDoc tags, lib/index.js structural conventions (MODULES/MAIN/EXPORTS markers), C header guard/define structure.
• Features with a clear majority (≥75%): file tree (100%), package.json top keys (100%), manifest.json shape (100%, byte-identical across all 67 packages), C header structure (100%), constant-identifier sub-heading uses #### (97%, this PR), ## See Also README section presence (78%, excluded — auto-populated), dbl keyword (87%), double keyword (91%), float64 keyword (85%), math/mathematics keywords (84%).
• Features without a clear majority: README var prefix convention (52% FLOAT64_-prefixed vs 40% bare in both README and lib, 8% split — no convention to enforce).

@stdlib/constants/float64/smallest-normal

README.md line 33: the FLOAT64_SMALLEST_NORMAL identifier sub-heading inside ## Usage is rendered at H5 (##### FLOAT64_SMALLEST_NORMAL) instead of H4 (#### FLOAT64_SMALLEST_NORMAL). The C-API counterpart in the same file (line 91, #### STDLIB_CONSTANT_FLOAT64_SMALLEST_NORMAL) already uses H4, as does the float32 sibling — so the H5 here is internally inconsistent and a typo, not an intentional deeper nesting. 97% conformance (65/67) for #### at this position across the namespace.

@stdlib/constants/float64/smallest-subnormal

README.md line 35: identical shape to smallest-normal. ##### FLOAT64_SMALLEST_SUBNORMAL inside ## Usage where 65 of 67 siblings, the same file's C-API section at line 97, and the float32 sibling all use ####. Same 97% conformance.

Related Issues

None.

Questions

No.

Other

Validation

• Structural extraction over all 67 packages: file trees, package.json and manifest.json shapes, README heading-level lists, README <section class="…"> wrappers, test/example filenames, C header structure.
• Semantic extraction over lib/index.js for each package: module-docblock and main-docblock JSDoc tag sets, MAIN var name, @example var name, // MODULES ///MAIN/EXPORTS section presence.
• Three-agent drift validation:
  • Agent 1 (opus, semantic-review) and Agent 2 (opus, cross-reference) (consolidated): verified no test, example, type declaration, REPL fixture, doc generator, or other consumer in the @stdlib tree references ##### FLOAT64_SMALLEST_NORMAL or ##### FLOAT64_SMALLEST_SUBNORMAL; the 5-hash heading appears nowhere outside these two READMEs.
  • Agent 3 (sonnet, structural-review) sampled pi, e, max, and both float32 siblings, confirming #### is the convention at the structurally identical position and that ##### → #### is the right repair.

Deliberately excluded

• Auto-populated sections: ## See Also README section (15 packages omit; section is generator-owned per project convention, content varies per package).
• Intentional deviations confirmed via float32-sibling cross-check (mirroring the convention documented in PR chore: update examples and add keyword #12967):
  • float64 keyword absent in exponent-bias, max/min-base{2,10}-exponent[-subnormal], precision — float32 siblings omit float32 in the same slot;
  • double/dbl keywords absent in gamma-lanczos-g, high-word-{abs,exponent,sign,significand}-mask, num-high-word-significand-bits, num-bytes, smallest-normal, smallest-subnormal — float32 siblings omit single/single-precision in the same slots and instead use the float/floatN/Nbit triplet;
  • math/mathematics keywords absent in max-safe-*, max-nth-*, min-safe-integer — float32 siblings omit; tagged as integer-bound constants by convention.
• Content-judgment fixes (not mechanical):
  • 11 packages missing a main-docblock @see URL (would require choosing a Wikipedia/OEIS/Mathworld reference per constant);
  • cbrt-eps, eps, sqrt-eps, fourth-root-eps, gamma-lanczos-g, glaisher-kinkelin README-vs-lib identifier mismatches (e.g., EPS in README, FLOAT64_EPSILON in lib): pre-existing inconsistency mirrored in constants/float32 per PR chore: update examples and add keyword #12967; reconciling requires a maintainer call on the canonical spelling and whether to carry the FLOAT64_ prefix in README usage blocks (52% prefixed vs 40% bare — no majority).
• Features without a clear majority dropped from drift analysis:
  • README usage-block var prefix convention (split 52/40);
  • Test count per package (87% have 2 tests, 13% have 3 — the third test is a definition-equivalence test that varies per constant and is intentional).
• Cross-run dedup: open PRs refactor: use constants/float64/nan in math/base/special/fibonacci #12154, refactor: use constants/float64/nan in stats/strided/dnanmeanpn #11768, feat: add constants/float64/inv-two-pi #8982 touch constants/float64 but do not modify either candidate file; no recent merged PR in the last 14 days touches smallest-normal/README.md or smallest-subnormal/README.md.

Cross-namespace tie-in

This run reuses the float32-sibling cross-check pattern from PR #12967 to drop intentional cross-namespace keyword omissions. The fix pattern "correct an H5 → H4 heading typo" is structurally identical to a propagation fix pattern; future runs can deduplicate by comparing heading-level distributions across precision-sibling namespaces.

Checklist

• Read, understood, and followed the contributing guidelines.

AI Assistance

• Yes
• No

If you answered "yes" above, how did you use AI assistance?

• Code generation (e.g., when writing an implementation or fixing a bug)
• Test/benchmark generation
• Documentation (including examples)
• Research and understanding

Disclosure

This PR was authored by Claude Code on behalf of @Planeshifter as an automated cross-package API-drift detection run against the @stdlib/constants/float64 namespace. Drift was identified by extracting structural and semantic features from every package, computing a per-feature majority pattern (≥75% threshold), and filtering candidate corrections through a three-agent validation pass plus a sibling cross-check against @stdlib/constants/float32 (PR #12967) to drop intentional cross-namespace deviations. A human will audit and promote the PR out of draft.

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@stdlib-js/reviewers

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Generated by Claude Code

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
constants/float64/smallest-normal	$\\color{green}62/62$ $\\color{green}+100.00\\%$	$\\color{green}1/1$ $\\color{green}+100.00\\%$	$\\color{green}0/0$ $\\color{green}+100.00\\%$	$\\color{green}62/62$ $\\color{green}+100.00\\%$
constants/float64/smallest-subnormal	$\\color{green}62/62$ $\\color{green}+100.00\\%$	$\\color{green}1/1$ $\\color{green}+100.00\\%$	$\\color{green}0/0$ $\\color{green}+100.00\\%$	$\\color{green}62/62$ $\\color{green}+100.00\\%$

The above coverage report was generated for the changes in this PR.