merge: upstream cinny v4.12.7 into lotus

Brings the 4.12.7 fixes: "%" sign wrapping below the composer input and
emoji autocompletion overwriting the preceding element. The release's
security half (sanitize-html, react-router-dom) was already applied in
91def3ad (we are on newer versions than upstream ships).

Resolved: kept our package.json/lockfile (the fork is ahead on every
dependency — React 19, router 7, i18next 26…), version 4.12.7-lotus, our
README/CONTRIBUTING, our "Lotus Chat vN" branding via pkg.version, and
the deleted GitHub-only workflows stay deleted. Note upstream announces
it is replacing matrix-js-sdk with its own SDK and pausing PRs; future
syncs will get harder.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

dev/oidc-test/README.md

@@ -39,6 +39,7 @@ services:
 ```
 
 ### 1a. MAS `config.yaml` — the parts that matter
+
 After `config generate` (which fills in `secrets.keys` + `encryption`), set:
 
 ```yaml
@@ -48,18 +49,19 @@ http:
 database:
   uri: postgresql://synapse:pw@postgres/synapse
 matrix:
-  homeserver: localhost          # the server_name
+  homeserver: localhost # the server_name
   endpoint: http://synapse:8008/
-  secret: "REPLACE_WITH_A_LONG_SHARED_ADMIN_TOKEN"
+  secret: 'REPLACE_WITH_A_LONG_SHARED_ADMIN_TOKEN'
 clients:
-  - client_id: "0000000000000000000SYNAPSE"
+  - client_id: '0000000000000000000SYNAPSE'
     client_auth_method: client_secret_basic
-    client_secret: "REPLACE_WITH_A_SHARED_CLIENT_SECRET"
-passwords:               # so you can create a local test account in the MAS UI
+    client_secret: 'REPLACE_WITH_A_SHARED_CLIENT_SECRET'
+passwords: # so you can create a local test account in the MAS UI
   enabled: true
 ```
 
 ### 1b. Synapse `homeserver.yaml` — delegate auth to MAS
+
 See `synapse-msc3861.yaml` in this folder; the key block is:
 
 ```yaml
@@ -67,17 +69,18 @@ experimental_features:
   msc3861:
     enabled: true
     issuer: http://localhost:8090/
-    client_id: "0000000000000000000SYNAPSE"
+    client_id: '0000000000000000000SYNAPSE'
     client_auth_method: client_secret_basic
-    client_secret: "REPLACE_WITH_A_SHARED_CLIENT_SECRET"   # == MAS clients[].client_secret
-    admin_token: "REPLACE_WITH_A_LONG_SHARED_ADMIN_TOKEN"  # == MAS matrix.secret
-    account_management_url: "http://localhost:8090/account"
+    client_secret: 'REPLACE_WITH_A_SHARED_CLIENT_SECRET' # == MAS clients[].client_secret
+    admin_token: 'REPLACE_WITH_A_LONG_SHARED_ADMIN_TOKEN' # == MAS matrix.secret
+    account_management_url: 'http://localhost:8090/account'
 ```
 
 Create a test user via the MAS UI (`http://localhost:8090/`) or
 `docker compose exec mas mas-cli manage register-user`.
 
 Sanity check discovery (the client relies on this):
+
 ```bash
 curl -s http://localhost:8008/.well-known/matrix/client | jq '."m.authentication"'
 # -> { "issuer": "http://localhost:8090/", "account": "http://localhost:8090/account" }
@@ -108,5 +111,6 @@ See **section N** of `../../LOTUS_TESTING.md` for the actual pass/fail steps
 revocation, account-management link, and the non-OIDC-regression check).
 
 ## Files here
+
 - `synapse-msc3861.yaml` — the Synapse experimental-features delta.
 - `config.local.json` — the Lotus `public/config.json` override.