docs: add missing intro section placeholders

[Planeshifter]

Description

This pull request:

• docs: insert the empty <section class="intro"> placeholder block in blas/base/ndarray/idamax, blas/base/ndarray/igamax, and blas/base/ndarray/isamax READMEs, bringing them in line with the rest of the namespace.

Namespace summary

• Target: @stdlib/blas/base/ndarray
• Members: 40 manually-maintained packages; no autogenerated members to exclude.
• Features extracted: file tree, package.json shape (top-level keys, scripts, keywords, directories, engines, os, dependencies), manifest.json shape, README section sequence (HTML <section> boundaries, ## / ### headings), test/, benchmark/, examples/ filenames, lib/main.js JSDoc tag shape, signature, require() set, and error-construction patterns.
• Features with a clear majority (≥75%): file tree (100% — identical 10/11-file layout), package.json top-level keys (100%), engines / os / directories / main / types / bugs / homepage (100% identical), 11 canonical keywords (100%: stdlib, stdmath, mathematics, math, blas, level 1, linear, algebra, subroutines, vector, ndarray), README ## Usage / ## Examples H2 sequence (100%), README HTML section sequence intro → usage → notes → examples → related → links (92.5%), lib/main.js JSDoc tags (license, param, returns, example) (100%), lib/main.js signature <pkg>( arrays ) (100%), 4 canonical require()s from @stdlib/ndarray/base/{numel-dimension,stride,offset,data-buffer} (100%), index.js description prefix BLAS level 1 routine to … (100%).
• Features without a clear majority (excluded): array keyword (22/40 = 55% — semantically split between scal/copy/swap/axpy and reduce/scan operations), ndarraylike2scalar require (32% — only when a scalar argument is unpacked), per-package equation <!-- <equation --> blocks (varies by math).

blas/base/ndarray/idamax

idamax is one of three outliers (idamax, igamax, isamax) missing the empty <section class="intro"> placeholder between the description blockquote and the usage section. 37 of the 40 namespace siblings carry the placeholder — 92.5% conformance — and the recently-opened srot package (PR #12510) adds it too, so the convention is current, not legacy. The fix is a six-line markdown insertion; no source or test change.

blas/base/ndarray/igamax

Same drift as idamax: the README jumps directly from the description blockquote to <section class="usage">, omitting the empty intro placeholder. The generic-typed g* sibling line (gasum, gaxpy, gcopy, gdot, gnrm2, gscal, gswap) all carry it. Mechanical six-line insertion.

blas/base/ndarray/isamax

Same drift as idamax and igamax. The single-precision s* siblings (sasum, saxpy, sdot, snrm2, sscal, sswap, etc.) all carry the placeholder. Mechanical six-line insertion.

Validation

Checked:

• Structural feature extraction across all 40 members (file tree, package.json keys/values, manifest.json keys where present, README HTML section sequence, README ## / ### heading sequence, test/benchmark/example filenames).
• Semantic feature extraction via lib/main.js source scan: signature shape, JSDoc tags, require set, throw / format presence (none in this namespace — base wrappers have no validation prologue).
• Three-agent drift validation on the surviving candidate: semantic, cross-reference, and structural reviewers all returned confirmed-drift for each of the three outliers.
• Pre-validation open-PR collision check via GitHub MCP: no open or recently-merged PR proposes the same intro-placeholder fix; the open srot (feat: add blas/base/ndarray/srot #12510) and drot (feat: add blas/base/ndarray/drot #12456) PRs add new packages and do not touch the three outliers' READMEs.

Deliberately excluded:

• The 3 packages with Copyright (c) 2025 (ddot, gdot, sdot) — copyright year reflects file-creation year by stdlib convention, not staleness; not drift.
• The array keyword distribution (22/40 = 55%) — semantically split between in-place vector ops and reductions; below the 75% threshold and the split is not random.
• Per-package equation <!-- <equation --> blocks inside the intro section — content is mathematics-specific (L1-norm, L2-norm, dot product) and not a structural drift.

Related Issues

None.

Questions

No.

Other

Generated by an automated cross-package drift-detection run (random-pick namespace selection; full per-feature distribution and dropped-candidate log live in the local report). The diff is mechanical: three READMEs gain six lines each of empty markdown placeholder; no source, test, or example file is touched; no observable behavior changes.

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 as part of an automated cross-package drift-detection routine. The drift was identified by structural feature extraction across @stdlib/blas/base/ndarray/; the proposed fix was validated by parallel semantic, cross-reference, and structural-review subagents (all returned confirmed-drift); the patch is a six-line markdown insertion in each of the three outlier READMEs.

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@stdlib-js/reviewers

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Generated by Claude Code

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
blas/base/ndarray/idamax	$\color{green}103/103$ $\color{green}+100.00\%$	$\color{green}3/3$ $\color{green}+100.00\%$	$\color{green}1/1$ $\color{green}+100.00\%$	$\color{green}103/103$ $\color{green}+100.00\%$
blas/base/ndarray/igamax	$\color{green}103/103$ $\color{green}+100.00\%$	$\color{green}3/3$ $\color{green}+100.00\%$	$\color{green}1/1$ $\color{green}+100.00\%$	$\color{green}103/103$ $\color{green}+100.00\%$
blas/base/ndarray/isamax	$\color{green}103/103$ $\color{green}+100.00\%$	$\color{green}3/3$ $\color{green}+100.00\%$	$\color{green}1/1$ $\color{green}+100.00\%$	$\color{green}103/103$ $\color{green}+100.00\%$

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