Preview: Replace instance exports with synthetic fixtures

.prettierignore

@@ -0,0 +1,2 @@
+# Sample source files of the preview's fixture repositories; they are content, not project code.
+dev/fixtures/repository/*/commit/

README.md

@@ -269,17 +269,25 @@ bun dev:forgejo:watch
 ```
 
 Open [http://localhost:3000](http://localhost:3000). The preview skips Forgejo's first-run setup, selects `github-auto`
-by default, and signs in automatically as `whereareiam`, including when a public page is opened first. Set
-`FORGEJO_PREVIEW_AUTO_LOGIN=false` to keep the normal sign-in page; the default credentials are `whereareiam` / `preview`.
-The watcher rebuilds the theme and restarts Forgejo
-after source changes so CSS and template updates are visible. The local Forgejo data is kept in the Docker volume
-`forgejo-dev-data`.
-
-The checked-in fixture snapshot under `dev/fixtures` restores `whereareiam/identica-docs` and the `arcadeya/devops`
-organization repository. It includes the recorded `identica-docs` Actions history as display-only data; no runner is
-configured and no workflow executes during seeding. It also restores the repositories' original creation times and
-their recorded public activity, including pushes, tags, and releases, so the profile activity timeline is useful for
-visual checks.
+by default, and signs in automatically as `alex`, including when a public page is opened first. Set
+`FORGEJO_PREVIEW_AUTO_LOGIN=false` to keep the normal sign-in page; the default credentials are `alex` / `preview`. The
+watcher rebuilds the theme and restarts Forgejo after source changes so CSS and template updates are visible.
+
+The first start fills the preview from the fixtures under `dev/fixtures`: the users `alex` and `sam`, the organization
+`acme`, and two repositories. `acme/webapp` has branches, tags, issues, pull requests in every state, releases including
+a draft and a prerelease, packages, and finished workflow runs with logs. `alex/notes` is nearly empty, for checking
+empty states. All of it is invented, and dates are written relative to the day of seeding, so the activity feed and
+contribution heatmap always look recent. No runner is configured and no workflow executes.
+
+The data is kept in the Docker volume `forgejo-dev-data`, and a repository that already exists is not seeded again.
+After changing a fixture, start from an empty volume:
+
+```bash
+bun dev:forgejo:reset
+bun dev:forgejo
+```
+
+See [`dev/fixtures/README.md`](dev/fixtures/README.md) for the fixture format.
 
 Override the local login before starting when needed:
 

dev/fixtures/README.md

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+# Preview fixtures
+
+Everything the local Forgejo preview shows comes from this folder. The content is invented; do not add exports from a
+real instance.
+
+```text
+dev/fixtures/
+  owner.json                 users, organizations and teams
+  repository/
+    <owner>-<name>/
+      repository.json        description, labels, milestones, issues, pull requests, releases, packages
+      history.json           commits, branches and tags
+      commit/<id>/           the files a commit adds or changes
+      action/<run>.json      one finished workflow run
+      action/<run>.log       that run's log
+```
+
+## Change what the preview shows
+
+Edit the files, then seed an empty volume. A repository that already exists in the preview is left as it is.
+
+```bash
+bun dev:forgejo:reset
+bun dev:forgejo
+```
+
+Seeding stops with a message naming the fixture when something does not line up, for example a pull request from a
+branch that `history.json` never creates. `bun vitest` runs the same checks without Docker.
+
+## Times
+
+Every time is written as `daysAgo`, optionally with a `time` of day in UTC, and is resolved when the preview is seeded.
+A time later than the moment of seeding is clamped to it.
+
+## Add a repository
+
+Create a folder under `repository/` with `repository.json` and `history.json`. Use an empty list for anything the
+repository should not have; `alex-notes` is the smallest example. The owner must be a user or organization in
+`owner.json`.
+
+## History
+
+Each entry in `history.json` becomes one commit. Its `id` names a folder under `commit/` whose files are copied over the
+working tree, so a commit only contains what it adds or changes. Commits are applied in list order. A `branch` seen for
+the first time starts at the default branch's tip at that point in the list; later commits on the same branch continue
+it. Tags name a commit `id`.
+
+Commit hashes differ between seeds because the dates do. Refer to commits by `id`, never by hash.
+
+## Issues, pull requests and releases
+
+- `author`, `assignees` and comment authors are user logins from `owner.json`.
+- `labels` and `milestone` must be declared in the same `repository.json`.
+- A pull request's `head` is a branch from `history.json`. Its `state` is `open`, `closed` or `merged`; a title starting
+  with `WIP:` makes it a draft.
+- A release's `tag` may be one from `history.json` or a new one, which a draft usually wants. Each entry in `assets` is
+  uploaded as a file with the given text content.
+- Packages are generic packages owned by the repository's owner.
+
+## Workflow runs
+
+Forgejo's API cannot create a finished run, so runs are written into the database. Each `action/<run>.json` lists its
+jobs and their steps with a status of `success`, `failure`, `cancelled` or `skipped` and a duration in seconds. The
+run's `commit` is a commit `id`, and for a `pull_request` event its `ref` is the pull request's branch. Each job also
+reports a commit status, which is what shows as the check mark beside the commit.
+
+The log beside it supplies the lines for every step:
+
+```text
+::job build
+::step Set up job
+docker(version:v9.1.0) received task of job build
+::step bun run build
+built in 412ms
+```
+
+`Set up job` and `Complete job` are steps Forgejo adds to every job by itself. List them to give them log lines and a
+duration; they are not stored as steps.
+
+## After a Forgejo upgrade
+
+The database rows for timestamps, the activity feed, workflow runs and commit statuses follow the schema of the Forgejo
+version pinned in `dev/docker-compose.yml`. When a column they write is missing or a new required column appears,
+seeding stops and names the table and column. Adjust the writers under `dev/preview/fixtures/database/`.