feat(rust): mod configuration from the site, and an editor that will not rewrite a float

R18's two tiers: a form generated from a config file's own values, and raw JSON
for what a form cannot express. Admin → Rust mod config, one live round trip per
action, nothing cached between a browser and a game host's disk.

`configEdit.js` is the part that could not be done naively. JavaScript cannot
tell `1` from `1.0`, and both mod frameworks deserialize a config into typed C#
classes — so a read-modify-write silently rewrites every whole-numbered float as
an integer on fields nobody touched, and a plugin that then throws at load does
not come back. It never parses, mutates and re-serialises: it records the SOURCE
SPAN of every value and splices literals into them, so an untouched `1.0` is
still `1.0` and a number an admin types travels as text the whole way (D35/D36).

The bridge's own config is editable with `Host`, `Port` and `ServerId` locked,
in the form and in the raw tier, because either would cut the link carrying the
edit or strand every row this site holds (D38). Credentials render masked with a
reveal; the raw tier shows them (D37) and the audit trail never does.

`rust_config_writes` records every save including the refused and the rolled
back — an operator asking why a setting is not what they set needs to see that
somebody tried.

Three defects a browser walk found that 179 green tests did not:

* every save of the bridge's own config was refused while the page said the
  opposite — a `<select>` whose value matches no `<option>` shows the first one,
  so the reload guess `RunicGateway` was on the wire and "nothing" was on the
  screen;
* `btn ghost` is not a class this platform defines (`.btn-ghost` is), so every
  secondary button in this module has rendered as a primary one since phase 7 —
  here it made the open file and the active tier indistinguishable;
* a save's refusal rendered at the top of a long form, far from the button.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PMH6bw1jXMgbyF3ZWGEzSM

client/src/api.js

@@ -147,6 +147,34 @@ export const adminPermissions = {
     req('/admin/rust/permissions/sync', { method: 'POST', body: serverId ? { serverId } : {} }),
 }
 
+// ── admin · mod configuration (R18) ───────────────────────────────────────
+//
+// Every call here is a LIVE round trip to a game host, which makes this the only
+// section of this file where a call can be slow, or fail because a server is
+// off. Nothing is cached anywhere between the browser and the host's disk: a
+// cached config is an edit an operator made over SSH that this website then
+// silently overwrote.
+//
+// `save` carries a `version` the host issued with the file. Send a stale one and
+// the answer is a 409 with the current file attached, rather than an overwrite
+// of whatever somebody else changed in the meantime.
+export const adminConfig = {
+  files: (serverId) => req(`/admin/rust/config/${encodeURIComponent(serverId)}/files`),
+
+  file: (serverId, path) =>
+    req(`/admin/rust/config/${encodeURIComponent(serverId)}/file${query({ path })}`),
+
+  // Two tiers, one route. `edits` is the generated form — pointers and literals,
+  // type-preserving — and `text` is the raw document. A number travels as TEXT
+  // in both: `1.0` parsed into a JavaScript number and sent back as `1` is the
+  // whole failure this feature was designed around.
+  save: (serverId, body) =>
+    req(`/admin/rust/config/${encodeURIComponent(serverId)}/file`, { method: 'POST', body }),
+
+  writes: (serverId, limit = null) =>
+    req(`/admin/rust/config/${encodeURIComponent(serverId)}/writes${query({ limit })}`),
+}
+
 // ── the admin.users.detail extension slot ─────────────────────────────────
 //
 // The client half of R13's first slot. Core hands the component a `userId` and
@@ -189,6 +217,7 @@ export default {
   playerLinks,
   admin,
   adminPermissions,
+  adminConfig,
   adminUserLinks,
   adminUserPermissions,
   BASE,