docs: sweep to the Anaconda 2026.06 baseline and measured container sizes

Docs are a release behind the containers and three of their claims about the images are wrong (2026-07 maintenance audit). The CHANGELOG half is closed and PLAN items 3/4/13 struck; no container-facing doc text has changed, so §1, §3 and §4 stand as filed.

1. Eight locations state the containers pin Anaconda 2025.12; both ship anaconda=2026.06

Ground truth: containers/quantecon/environment.yml:11, migrated in #95. The lean image carries the matching anaconda=2026.06 linux-64 py313 (MKL) pin set (comment at containers/quantecon-build/environment.yml:12-19, pins from :20) — same baseline.

Stale: containers/README.md:18, containers/quantecon/README.md:15 and :107, containers/quantecon-build/README.md:26 and :82, docs/ARCHITECTURE.md:12, docs/CONTAINER-GUIDE.md:9.

PLAN.md is now clear: the dependency policy was corrected in #139 and PLAN.md:14 in #127, leaving only the deliberate narration at PLAN.md:68 of the date-pin misconception that produced #86/#87.

CHANGELOG excluded — its 2025.12 mentions at CHANGELOG.md:254, :260 and :553 are correct historical record, and :260-261 retro-annotates the 2026.06 move.

2. CHANGELOG — closed

The #28 entry was rewritten in past tense and retro-annotated at CHANGELOG.md:254-261; #95 landed at CHANGELOG.md:203-207, #90 at :208-209, #94 at :210 — all in v0.9.0 (#113). #91 (rewrote PLAN.md and README.md) and #93 (added PROJECT-OPTIMIZE-PREVIEWS.md plus a README index link) were dropped as docs-only planning edits; the repo has not changelogged the equivalent since (#130 and #133 are unlogged PLAN.md edits).

3. Six docs still advertise "~8GB / ~3GB" and "~60% smaller"

Measured — already correct at README.md:147-148, docs/ARCHITECTURE.md:15 and :53, docs/CONTAINER-GUIDE.md:9-10, fixed there by the v0.8.0 sweep (CHANGELOG.md:337-339) and nowhere else — is 8.3 GB / 7.1 GB on disk (~3.2 / ~2.9 GB compressed): a ~14% saving, not 60%.

Nine stale sites: docs/QUICK-REFERENCE.md:22-23, setup-environment/README.md:34-35, containers/README.md:9-10 and :35 (the one surviving "~60% smaller"), containers/VALIDATION.md:17-18, containers/quantecon-build/README.md:18 and :79, .github/copilot-instructions.md:33-34 and :134.

Do not copy the pair forward unchanged: v0.11.0 changed the measurement basis (#108) — the size job at .github/workflows/test-container.yml:97-101 now reads the registry manifest and reports compressed layer bytes, a smaller number not comparable with the old docker images series (CHANGELOG.md:83-84; same warning at .github/workflows/test-container.yml:73-76).

4. "Minimal TexLive" is false

Diffing the apt lists at containers/quantecon/Dockerfile:8-44 against containers/quantecon-build/Dockerfile:9-45 gives exactly two differences: the lean image drops texlive-luatex (containers/quantecon/Dockerfile:15) and adds graphviz (containers/quantecon-build/Dockerfile:32); texlive-latex-extra and texlive-fonts-extra are in both. LaTeX dominates both, hence the small size gap; the claim is the stated reason for the lean image and the basis of every "use quantecon-build for CI" recommendation. Stale at containers/README.md:33, containers/quantecon-build/README.md:15, containers/VALIDATION.md:18 and .github/copilot-instructions.md:34.

5. PLAN.md and CONTRIBUTING.md

Items 3/4/13 are struck with closure notes at PLAN.md:68, :51 and :70 (#130). Left: the "Open issues disposition" table at PLAN.md:108-117 carries rows only for #83, #123, #14, #29, #30, #18, #27 and #2 — nothing opened since the July 2026 review. The doc-update matrix at CONTRIBUTING.md:129-134 lists only the action README.md, docs/QUICK-REFERENCE.md, docs/MIGRATION-GUIDE.md and docs/FUTURE-DEVELOPMENT.md — no PLAN.md row, which lets the backlog drift between audits.

Checklist

• 2025.12 → 2026.06 across the seven locations in §1
• Rewrite the #28 [Unreleased] CHANGELOG entry in past tense — done in v0.9.0 (#113)
• Add [Unreleased] entries for #95, #90 and #94 — done in v0.9.0 (#113); #91 and #93 dropped as docs-only planning edits
• Re-measure both images from the current manifests, propagate the pair to the nine sites in §3 stating which metric it is, and delete "~60% smaller" and the "faster CI pulls" / "faster pull" claims
• Correct the "Minimal TexLive" wording in the four files in §4
• Strike PLAN items 3/4/13 — done in #130
• Add disposition rows for the issues opened since the July review: #92, #96, #97, #98, #99, #100, #102, #105–#110, #115, #129, #135
• Add a PLAN.md row to the CONTRIBUTING doc-update matrix

Sequencing

docs/QUICK-REFERENCE.md and setup-environment/README.md are also edited by #109 (#99 folded into it), and PLAN item 10 at PLAN.md:80 carries "Propagate corrected container-size figures everywhere" over the same files — land them as one docs PR, not three passes.

Start by reading the listed stale passages and the measurement logic in .github/workflows/test-container.yml:73-76 and :97-101, then check the overlap with #109 and PLAN.md:80. Update the seven baseline references, nine size sites, four TexLive claims, issue-disposition rows, and CONTRIBUTING.md:129-134. Done means all unchecked checklist items are resolved without changing historical CHANGELOG entries or duplicating #109's work.