Rename Installation to Instance

Follows the portal: the noun is "instance" everywhere the app says it —
UI strings, CLI output, error details, docs and comments. The wire keys
(`instance_id`, `instance_token`) and the hub route this calls move with it.

An existing cloud.json is adopted rather than refused: without the key
alias the dataclass fails to parse, which the caller swallows and reads as
"never enrolled" instead of "reconnect".

`instance_key` on a node type becomes `target_key`. It means the outside
thing a node points at, which is a different sense of the word, and keeping
both would put two meanings of "instance" in one codebase.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015YrQnKV3bnQd4K342y8tKj

docs/interface/index.md

@@ -1,12 +1,12 @@
 # The dashboard app
 
 The web interface is a single-page app served at `app.${DOMAIN}` — or, for an
-installation reached through a portal, at `${DOMAIN}/i/{installation-id}`.
+instance reached through a portal, at `${DOMAIN}/i/{instance-id}`.
 Either way it is the same application, and it is a client of the same REST API
 you can script against.
 
-Sign in with the account the installation was created with. On a fresh
-installation that account was printed once, on the first start.
+Sign in with the account the instance was created with. On a fresh
+instance that account was printed once, on the first start.
 
 ## The shell
 
@@ -22,7 +22,7 @@ phone the sidebar collapses to a sheet.
 | **Modules** | the Python packages your node code may import |
 | **Alerts** | where failures get sent |
 | **Admin** | users (superusers only) |
-| **Search** | anything in this installation, by name |
+| **Search** | anything in this instance, by name |
 | **Settings** | your account, appearance, and remote access |
 
 ### Search
@@ -33,8 +33,8 @@ dashboards and the widgets on them, panels, secrets, modules, workers and alert
 channels. Picking a node opens its flow with that node in focus; picking a
 widget opens its dashboard.
 
-It searches this installation. Reached through a portal, other installations
-are behind **All installations** at the top of the sidebar.
+It searches this instance. Reached through a portal, other instances
+are behind **All instances** at the top of the sidebar.
 
 ## Home
 
@@ -44,7 +44,7 @@ The one screen you leave open. Four things share it.
 
 Every flow drawn as a neuron, wired to the flows it exchanges messages with.
 This is the brand mark made live, and it is also the fastest read on the
-installation: a neuron pulses when its flow is running work, and its ring turns
+instance: a neuron pulses when its flow is running work, and its ring turns
 terracotta when the flow cannot run as written. A neuron with a problem keeps
 its label showing so you can see which one it is without hovering.
 
@@ -70,7 +70,7 @@ Always answers, degraded or not. The tiles cover:
   because their graph does not validate
 - **Nodes** — how many failed to load
 - **Runs running** — batch runs in flight right now, and how many are
-  waiting. Only on an installation that has run something
+  waiting. Only on an instance that has run something
 - **Queue** — depth, and how old the oldest pending item is
 - **Loop lag** — whether the engine's event loop is keeping up
 
@@ -110,8 +110,8 @@ so does Escape. The Dashboards screen works the same way.
 - [Dashboards and panels](dashboards.md) — widgets, bindings, and hanging a
   screen on a wall
 - [Secrets, modules and alerts](operations.md) — the three screens that keep an
-  installation running
-- [Accounts and the portal](portal.md) — reaching an installation from outside
+  instance running
+- [Accounts and the portal](portal.md) — reaching an instance from outside
   its network
 
 ## Appearance