chore(changelog): collect unreleased entries in changelog/unreleased/ (#47)

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

changelog/README.md

@@ -1,10 +1,10 @@
 # Changelog Details
 
-The root [../CHANGELOG.md](../CHANGELOG.md) keeps one brief line per release. Each release owns a folder here:
+The root [../CHANGELOG.md](../CHANGELOG.md) keeps one brief line per release. Work in progress lives in [`unreleased/`](unreleased/); each shipped release owns a numbered folder here:
 
-- `<version>/README.md` — the release summary: one brief line per change, each linking its detail file, e.g. `- [YYYY-MM-DD] Brief description. ([details](YYYY-MM-DD-short-slug.md))`
+- `<folder>/README.md` — the summary: one brief line per change, each linking its detail file, e.g. `- [YYYY-MM-DD] Brief description. ([details](YYYY-MM-DD-short-slug.md))`
-- `<version>/YYYY-MM-DD-short-slug.md` — one detail file per entry, named by the entry date: an H1 title, then what changed and why, using `##` sections once the entry covers more than one thing.
+- `<folder>/YYYY-MM-DD-short-slug.md` — one detail file per entry, named by the entry date: an H1 title, then what changed and why, using `##` sections once the entry covers more than one thing.
 - Entries are grouped by the surface they change — Models, Web App, landing site, skills, docs, tooling — rather than one file per commit. A related change extends the existing file and its summary line instead of opening a new one.
-- Changes not yet released go into the upcoming version's folder; during release preparation, rename the folder if the number changed and add the release line to the root file. Released folders are frozen.
+- Unreleased changes go in `unreleased/`, never in a numbered folder: the next version number is not knowable while the work is being written — the batch that accumulated as `0.2.0/` shipped as 0.1.1 — so a guessed number only creates a rename to get wrong later. At release, rename `unreleased/` to the version actually shipped, swap its `# Unreleased` heading for `# Version X.Y.Z` plus a `Released on <date>.` line, add the release line to the root file, and create a fresh empty `unreleased/`. Released folders are frozen.
 
 Written in English. History starts after the v0.0.1 release (2026-07-19); earlier changes are not backfilled.

changelog/unreleased/README.md

@@ -0,0 +1,3 @@
+# Unreleased
+
+Changes since v0.1.1. The version number is assigned at release, when this folder is renamed.