docs(openspec): archive fpagent-installer-multiarch and sync specs

Bundle selection is now architecture-aware, not just codename-aware, and the
no-compatible-bundle failure names the host architecture. Merged into the
fpagent-installer spec and archived the change.

openspec/changes/archive/2026-10-06-fpagent-installer-multiarch/proposal.md

@@ -0,0 +1,47 @@
+# Proposal: fpagent-installer-multiarch
+
+## Why
+
+The hosted installer only ever picks the x86_64 bundle. fingerprint-agent
+v1.5.0 publishes a 32-bit `-linux-i386` bundle and its own installer accepts
+i386 hosts, so a 32-bit field laptop running the public one-liner fails with
+"no compatible bundle" and installs nothing, even though a matching release
+asset exists.
+
+## What Changes
+
+- The installer detects the host architecture (`uname -m` → `x86_64` or
+  `i386`) and selects the matching bundle: the distro-codename bundle when one
+  exists for that architecture, else the generic `-linux-<arch>` bundle.
+- An unsupported architecture fails with a message that names the host machine,
+  and installs nothing.
+- The version parsed from the asset name accepts the `-linux-i386` suffix, so a
+  32-bit install records and reports its version the same way x86_64 does.
+- The installer's help text matches the bundle installer: the systemd service
+  and the self-update timer are on by default, so `--no-service`,
+  `--no-updates` and `--update-base` are documented instead of
+  `--enable-service` being described as required to get a service.
+
+## Capabilities
+
+### New Capabilities
+
+(none)
+
+### Modified Capabilities
+
+- `fpagent-installer`: bundle selection becomes architecture-aware (not just
+  distro-codename aware), the no-compatible-bundle failure names the host
+  architecture, and the version is derived for every published architecture.
+
+## Impact
+
+- `tools/public/fpagent/install.sh`: architecture detection, bundle pick,
+  version regex, help text.
+- `tools/test/fpagent-install.test.js`: architecture selection and version
+  parsing tests.
+- `README.md`: the installer section (flags and architectures).
+- Depends on the `fingerprint-agent` bundle naming
+  `fpagent-<version>-linux-<arch>.tar.gz`, where `<arch>` is `x86_64` or
+  `i386` (v1.5.0 and newer). No change to `tools/server.js`: the server proxies
+  whatever assets the release lists.