docs: a release procedure from a green main to tagged, packaged artifacts (closes #387)

Add docs/RELEASE.md, linked from README.md's Release Artifacts section, giving
the release procedure as a numbered list: confirm main is green in CI, confirm
the one version in package.json and the two manifests matches the intended tag,
make package from a clean checkout, verify SHA256SUMS, create the annotated tag
vX.Y.Z, then distribute per browser. Each step names who performs it, marks the
owner-only ones, and states the check that it worked. Every repo command cited
(make setup, make check, make package) exists on next; tagging and verification
use standard git and coreutils, and the CRX pack line is README's own.

The per-browser distribution step is written as pending the owner's choice on
issue 386, with the Firefox and Chrome options named but none presented as
settled. Docs only: no code or test changes.

Model: opus-4-8

TODO.md

@@ -58,6 +58,16 @@ but the review is broader than any of them.
   approve, reject and disconnect paths against a transaction approval
   broadcasting behind them: each is declined and the dApp still receives its
   broadcast result.
+- 2026-09-21: `docs/RELEASE.md`, linked from `README.md`, states the release
+  procedure as a numbered list a newcomer can follow: confirm `main` is green in
+  CI, confirm the one version in the three files matches the intended tag,
+  `make package` from a clean checkout, verify `SHA256SUMS`, tag `vX.Y.Z`, then
+  distribute per browser. Each step names who performs it (owner-only steps
+  marked) and the check that it worked. The distribution step is written as
+  pending the owner's choice on
+  [#386](https://git.eeqj.de/sneak/AutistMask/issues/386), with the Firefox and
+  Chrome options named but none settled. Docs only
+  ([#387](https://git.eeqj.de/sneak/AutistMask/issues/387)).
 
 - 2026-08-30: An address no longer wraps, or is shortened to fit, in any of the
   common views ([#380](https://git.eeqj.de/sneak/AutistMask/issues/380)). The