docs: put the contributor surfaces on the 2.x vocabulary

[DemchaAV]

Why

A contributor following CONTRIBUTING.md writes code that does not compile.

Its "new built-in template" section routes authors to BusinessTheme, InvoiceTemplateV2 and ProposalTemplateV2; its engine-primitive section tells them to add a container-growth marker and Breakable to an Entity, with geometry in EntityBounds and propagation in ParentContainerUpdater. All seven types were removed in 2.0 — checked one by one against src/main, none survive. The linked ComputedPositionTest does not exist either.

The same drift runs through the release-facing surface. ROADMAP.md still described 2.1 as "in development on develop, building toward the 2.1.0 minor" and 2.0 as the current stable line, five days after v2.1.0 was tagged and published. docs/README.md listed five superseded 1.x minor-to-minor upgrade guides on its main path and did not link migration/v2.0.0-modules.md at all — the only migration guide that applies to anyone arriving today.

And the example catalogue is stated four times with four different numbers: examples/README.md says 63 twice, CONTRIBUTING.md says 54, the release runbook expects "26+ Generated: lines". GenerateAllExamples invokes 94.

What changed

Retired API. The two template-authoring paths collapse to the one that exists: the layered stack, every preset a final class with a create(BrandTheme) factory, reference implementations named. The engine-primitive section describes the real pipeline — a NodeDefinition that prepares and measures, pagination declared on the definition rather than by a marker, continuation through SplittableLeafCompiler, and container growth as a consequence of what children report during prepare rather than a separate signal. The "Keep the entity core thin" block is deleted outright; every bullet in it named an absent type.

PPTX backend location. CONTRIBUTING.md (repository map and package roots), SECURITY.md (in-scope list) and docs/architecture/overview.md (package roots) described the pptx module as a semantic exporter. Its primary backend is fixed-layout — document.backend.fixed.pptx, consuming the same resolved LayoutGraph as the PDF backend — alongside the older semantic manifest skeleton, and both are now named. The handler-registration rule gains its second half: a new fragment kind must register with PdfFixedLayoutBackend and PptxFixedLayoutBackend, or it renders in one output and silently vanishes from the other.

This is deliberately not a sweep. PptxSemanticBackend still exists and render-pptx/README.md, docs/architecture/package-map.md and render-pptx/pom.xml describe it correctly; only the places calling it the module's primary surface are touched.

Release surface. ROADMAP.md promotes 2.1 to current stable, demotes 2.0 to history, and points ## Now at what follows. The README release-status block describes 2.1.1's own content instead of carrying 2.1.0's headline forward with the version number. docs/README.md leads with the guides that apply and folds the historical ones behind a <details>.

Templates and routing. bug_report.md is rewritten: the reproduction now uses try-with-resources and calls buildPdf() — as shipped, a repro pasted from the template rendered nothing — and ## Environment asks for the output backend, the modules on the classpath and the font source rather than a hardcoded PDFBox: 3.0.7, with a new ## Generated artifact section accepting a layoutSnapshot(). feature_request.md swaps BusinessTheme for BrandTheme and lists each anchor with its package (all verified present). pull_request_template.md gets the lanes the repository actually has and stops requiring a hand-updated gallery count. A new ISSUE_TEMPLATE/config.yml routes usage questions to Discussions, which are enabled and were not linked from anywhere.

Counts removed, not synchronised. examples/README.md, CONTRIBUTING.md, web/index.html and the release runbook. A number in prose has no owner and no guard.

Runbook. One gate grepped README.md for [0-9]+ green tests — the README makes no such claim, so it always passed. Another compared examples/README.md gallery rows against *Example.java files: 48 against 100, already failing. Three items pointed at docs/migration-v1-N-to-v1-M.md, a path that moved to docs/migration/. The gallery gate becomes a ShowcaseMetadata coverage check, and a new item covers ROADMAP.md.

README structure. The comparison block moves below ## Architecture — same file, no discovery lost — so it stops sitting between the first working example and the next step. ## What's new in 2.0 compresses from thirteen lines to its two links. The documentation catalogue collapses from four sub-lists to four routes, gaining ROADMAP.md and SUPPORT.md, which the landing page never linked. 372 → 361 lines.

Two files fixed beyond the original scope, because #474 made them stale an hour before this branch: CONTRIBUTING.md:32 listed the pre-#474 guard names with no -pl scope, and :73 claimed a docs-only PR "runs the guards only", which is no longer how the paths filter behaves.

Verification

./mvnw -B -ntp clean verify -pl :graph-compose-core,:graph-compose-render-pdf,:graph-compose-render-docx,:graph-compose-render-pptx,:graph-compose-templates,:graph-compose-testing,:graph-compose,:graph-compose-bundle,:graph-compose-qa,:graph-compose-coverage -am

BUILD SUCCESS, 13/13 modules, 2:01, zero failures.

Claims were checked rather than assumed:

Claim	How
Seven named types are gone	grep for each declaration across every src/main — all absent
ComputedPositionTest is a dead link	find — absent; repointed at LayoutInsetsTest
Three "Planned for v1.6" rows shipped	CanvasLayerNode, ListBuilder.addItem(String, …), DocumentTableCell.node(DocumentNode) all present
The real example count	94 generate() invocations, 100 *Example.java files, 48 gallery rows
Every anchor a feature-request author is sent to	each type located in src/main
The qa guard command in CONTRIBUTING.md	run: 12 + 4 tests, BUILD SUCCESS
Links and anchors	every relative link across the 16 files, and every #anchor in the restructured README, resolves

The documented qa command was run on a warm ~/.m2, which is exactly its trap: a standalone -f qa/pom.xml resolves its graph-compose-* dependencies from the local repository rather than the reactor, so without a prior install it quietly tests the last artifacts you installed instead of your working tree. That precondition is now part of the instruction.

One decision to confirm

ISSUE_TEMPLATE/config.yml sets blank_issues_enabled: false. That is what forces the routing — every report goes through a template or a contact link — but it removes the blank-issue escape hatch, and it is the only behavioural change here rather than a textual one. Happy to flip it to true and keep just the contact links.

Not in scope

docs/contributing/implementation-guide.md still describes the removed execution layer and carries dead source links. Rewriting it is its own change; this PR demotes it from "read these files first" to background reading and adds package-map.md in its place.

Nothing here is machine-checked: no guard scans SECURITY.md, SUPPORT.md, ROADMAP.md or .github/**, and none of the retired symbols are on a forbidden-token list, so every correction in this PR can silently return. Closing that is the next change in this series.