Docs: sweep stale references and inconsistencies (#40)

[mmcky]

Closes #40 (D24–D34) — fixes dead references and inconsistencies across the docs.

Dead/stale references fixed

• D24 — containers/VALIDATION.md described a three-stage builder pipeline (test-html-builder.yml, …) that doesn't exist → replaced with the real test-containers-lectures.yml + test-container.yml.
• D25 — build-jupyter-cache/README.md referenced a non-existent cache-standard.yml.
• D26 — docs/ARCHITECTURE.md repo tree listed non-existent Dockerfile.gpu / environment-gpu.yml → replaced with the real quantecon + quantecon-build layout.
• D30 — refreshed the stale README status line.
• D33 — fixed a mangled code fence in TESTING.md.
• D29 — documented failure-artifact-name (and corrected output-dir) in QUICK-REFERENCE.md.
• D28 — MIGRATION-GUIDE.md no longer presents the non-container path as the recommendation.
• Bonus — README usage examples used @main → switched to @v0 (the C1 sweep only touched @v1).

Previously-flagged judgment calls — now resolved

• D27 (container sizes) — measured, not guessed. Pulled both images (amd64) and read the sizes: lean 7.14 GB / full 8.34 GB on disk; 2.85 GB / 3.24 GB compressed pull. The old "lean ~3 GB vs full ~8 GB" was mixing metrics (compressed-lean vs on-disk-full), implying a size gap that doesn't exist — LaTeX + the scientific stack dominate both, so "lean" is only modestly smaller. All size mentions now state both metrics explicitly.
• D31 (consuming-repo list) — removed. Per maintainer, the per-repo list is a maintenance burden; replaced with a pointer to QuantEcon/meta#321, which will track it centrally.

Notes

• D32 (duplicate build-time tables) turned out moot — VALIDATION.md has no build-time table.
• Docs-only; no action behavior changes.

Closes #40

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Docs-only cleanup addressing issue #40 by removing stale/dead references and aligning documentation with the repository’s current workflows, templates, and release/versioning guidance.

Changes:

• Replaced dead/fictional workflow and template references across docs with the current, real workflows/templates (e.g., container validation + cache template references).
• Standardized and refreshed documentation details (release status, @v0 usage examples, container layout/sizing notes).
• Fixed a broken markdown code fence in TESTING.md and updated quick-reference inputs.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
TESTING.md	Fixes a mangled code fence in troubleshooting docs.
README.md	Updates status line and switches usage examples to @v0; refreshes “Usage by Repository” list.
docs/QUICK-REFERENCE.md	Updates build-lectures example (output-dir) and documents failure-artifact-name.
docs/MIGRATION-GUIDE.md	Clarifies container-first recommendation while keeping setup-environment example.
docs/CONTAINER-GUIDE.md	Documents both container images and aligns sizing/pull-time narrative.
docs/ARCHITECTURE.md	Updates repo tree and container sizing, but still contains internal inconsistencies (see PR comments).
containers/VALIDATION.md	Replaces fictional multi-workflow pipeline description with the current testing workflows.
CHANGELOG.md	Adds an Unreleased entry summarizing the doc sweep.
build-jupyter-cache/README.md	Removes reference to a non-existent workflow template (cache-standard.yml).