Release notes: the 2.0.0 notes guide an upgrade from 1.x, which 2.0.0 does not offer #502

cargo xtask release 2.0.0 publishes the [Unreleased] section of CHANGELOG.md, with the 2.0.0 fragments folded in after the entries already there. 1.0 and 1.1 cannot be upgraded to 2.0.0 (#490, #498), but folded on main (43dfa79) the notes guide an upgrade from them anyway, and some of their text is stale.

Upgrade guidance, for an upgrade there is none of

• 22 upgrade notes: configuration keys to remove and values to set again, URLs and .npmrc lines to update, the helm upgrade from Redis to Valkey, the chart's new name, renamed labels and User-Agent values to match, and so on. The fresh-install note (Release notes: say that 2.0.0 is a fresh install that does not upgrade a 1.x database #490) and the database note (Migrations: squash 0001–0049 into one 2.0.0 baseline, and refuse a database of an earlier build #498) come 17th and 18th of them, because the fold orders them by issue number, and Release notes: say that 2.0.0 is a fresh install that does not upgrade a 1.x database #490's note itself explains how to move a 1.x install over.
• The upgrade notes open with "Migration 0036 adds the nexus_import and nexus_import_item tables for imports from Nexus; it changes no existing data." Since Migrations: squash 0001–0049 into one 2.0.0 baseline, and refuse a database of an earlier build #498 there is no migration 0036.
• A docker group's writable_member is stored by name: renaming or deleting that repository breaks group pushes, and a later repository with the old name silently becomes the push target #219 (Fixed): "migration 0037 converts existing groups; a name no hosted docker repository has any more is dropped … Downgrading to 1.1.0 leaves docker groups without a writable member until it is set again."
• Workload registry tokens: one minted from a forge_wif. key works again once the reaper deletes the key's row, and one minted from a CI token directly dies with that token's key #201 (Fixed): "Registry tokens issued before the upgrade are refused once, and clients ask for a new one."

Stale

• Raw repositories as a format plugin: a file store in the plugin contract #431 (Features) describes raw repositories as plugins/raw with a plugin.toml (storage = "files") under the WebAssembly contract forge:format@0.4.0, and says "/raw answers as before". Move the format crates from plugins/<id> to crates/formats/<id> #443, Describe each format in Rust and remove plugin.toml #444 and Remove WebAssembly format plugins and wasmtime: built-in plugins only #437 moved and removed those, and Serve every repository at /repository/{name}/, with no format in the URL (breaking) #438 serves raw at /repository/<name>/.
• Import from Nexus per repository: copy a hosted repository's packages into Forge, resumable and verified #183 (Features): the Nexus import copies "NuGet packages, Helm charts, and Docker images"; since Helm charts: classic chart repositories and OCI charts #43 it copies NuGet and Docker only (docs/nexus-import.md).
• The links of the entries that were in [Unreleased] before the fragments, and the [Unreleased] compare link the fold takes its links from, point to schmitch/forge rather than forgepkg/forge; the changelog's header still calls the project envisia-forge.

Fix

Fold the fragments with cargo xtask changelog 2.0.0 in a pull request of its own, as DEVELOPMENT.md (Changelog entries) describes, and edit the notes: an introduction for 2.0.0, one upgrade note saying that 1.0 and 1.1 cannot be upgraded (and that startup refuses their database), no other upgrade guidance, the stale text fixed, and links to forgepkg/forge.