docs: record §10 onboarding bullet in ADR 0023; trim changelog

CHANGELOG.md

@@ -16,14 +16,13 @@ See [ADR 0009](./adr/0009-methodology-as-versioned-dependency.md).
 ### Added
 
 - **One-command onboarding** — §10 gains a bullet: a substantial project
-  bootstraps from clone to a working environment with one documented,
+  bootstraps from a clone to a working environment with one documented,
   reproducible command; "works on my machine" is a defect in the
-  onboarding path. The developer entry point is the one thing §6/§10's
-  reproducible-build guidance left unsaid. Added as a sub-bullet, not a
-  new practice — the one idea from the (withdrawn) PR #22/#24 expansion
-  exchange that cleared the bar, captured at the right scale. *Adoption:
-  reference-only; optionally add a one-command setup where a substantial
-  project lacks one.*
+  onboarding path. The tool stays the project's choice (no mandate). The
+  developer entry point is the one thing §6/§10's reproducible-build
+  guidance left unsaid; recorded as a sub-bullet, not a new practice
+  (ADR 0023). *Adoption: reference-only; optionally add a one-command
+  setup where a substantial project lacks one.*
 
 ## [0.11.0] - 2026-06-20
 

adr/0023-one-command-onboarding-in-section-10.md

@@ -0,0 +1,80 @@
+# ADR 0023: One-command onboarding added to §10
+
+- **Status:** Accepted
+- **Date:** 2026-06-21
+- **Deciders:** vpc
+
+## Context
+
+§10 (Dependencies are decisions) was established by ADR 0003 as exactly
+three bullets: adding-is-a-decision, lockfiles-committed, updates-deliberate.
+Version 0.12.0 (PR #25) added a **fourth, normative** bullet —
+"one-command onboarding; 'works on my machine' is a defect" — but shipped it
+**without an ADR**, asserting scale-to-work.
+
+A PR review flagged the governance gap, and it is real. The methodology's own
+rules require it:
+
+- *"If a practice changes, update the relevant document and record the change
+  in an ADR."* ("Changing this document")
+- *"If you find yourself arguing for or against a practice that isn't listed
+  here, that is a sign you need an ADR, not a longer methodology doc."*
+
+PR #25's body was precisely an argument for a practice (it cited the withdrawn
+#22/#24 exchange). And the precedent is consistent: comparably-scoped additions
+in this repo got ADRs — ADR 0014 (a decision-guide row), ADR 0016 (a
+postmortem home). Without this record, §10 carried a normative bullet no ADR
+traced to — the doc/decision drift §1 exists to prevent. ADR 0003 is
+append-only, so the new bullet is recorded **here**, not by editing it.
+
+## Decision
+
+Record the §10 **one-command onboarding** bullet as an accepted extension of
+ADR 0003's Dependencies practice:
+
+> A substantial project bootstraps from a clone to a working environment with
+> a single documented, reproducible command; "works on my machine" is a defect
+> in the onboarding path. The tool (`make setup` / devcontainer / Nix flake) is
+> the project's choice — **no tooling mandate**, consistent with ADR 0003's
+> "weigh and record, not a particular tool."
+
+§10's decision trail is now **ADR 0003 + this ADR** together. The bullet is the
+one survivor of the withdrawn #22/#24 expansion exchange, kept at sub-bullet
+scale rather than as a new numbered practice.
+
+## Alternatives considered
+
+- **Leave the bullet unrecorded** (rely on scale-to-work alone) — rejected: a
+  normative §10 bullet with no ADR is the exact drift §1 prevents, and the
+  precedent (0014/0016) records comparable additions.
+- **Revert the bullet** — rejected: the developer entry point is the one thing
+  §6/§10's reproducible-build guidance genuinely left unsaid, and the owner
+  chose to keep it.
+- **Edit ADR 0003's Decision list to add the bullet** (the reviewer's
+  alternative) — rejected: ADRs are append-only; you supersede or record
+  anew, never edit.
+
+## Consequences
+
+- §10 is traceable to its decisions again.
+- A small, deliberate precedent: a normative sub-bullet that extends a practice
+  gets a short ADR — honoring the "arguing for a practice → ADR" rule without a
+  whole new practice.
+- Cheap to reverse: revert the bullet and supersede this ADR.
+
+## Adoption impact
+
+**Reference-only.** The bullet already shipped in 0.12.0; this ADR records the
+decision behind it. Nothing for consuming projects to do.
+
+## References
+
+- ADR 0003 (`adr/0003-dependencies-are-decisions.md`) — the §10 practice this
+  extends; `methodology.md` §10, §1, "Changing this document."
+- ADR 0014, ADR 0016 — precedent: comparably-scoped additions recorded by ADR.
+- PR #25 (the bullet) and its review (the flagged governance gap).
+
+---
+
+> Following the format proposed by Michael Nygard in
+> [Documenting Architecture Decisions](https://cognitect.com/blog/2011/11/15/documenting-architecture-decisions).