Rename setups and add provider reauthentication

EXPLORER.md

@@ -14,7 +14,7 @@ AGENTS.md. `server/src/files.rs` is the backend and `FilesScreen.kt` /
 ## What it is, in one paragraph
 
 A machine's filesystem, seen from the phone through the backend. The explorer
-belongs to a **setup** (a machine), not to a session: a session only says
+belongs to a **machine** (a machine), not to a session: a session only says
 where to start. Every operation — list, read, write, create — is one shell
 script run through `Transport`, exactly the way the import listing and the
 usage fetch already work, so the local and the ssh case are one
@@ -25,16 +25,16 @@ message. The phone draws what came back.
 
 ### 1. Keyed on the machine, opened from the session
 
-Routes live under `/setups/{id}/…`, beside `importable`, because a filesystem
+Routes live under `/machines/{id}/…`, beside `importable`, because a filesystem
 is a property of a machine. The session screen's folder button opens the
-explorer with the session's setup and its `cwd`; a session with no `cwd`
+explorer with the session's machine and its `cwd`; a session with no `cwd`
 opens at the machine's home, which the **machine** resolves (`cd` with no
 argument and `pwd -P`), never a path the phone guessed. Nothing in the
-explorer knows what a session is, so a later entry point from the setups tab
+explorer knows what a session is, so a later entry point from the machines tab
 is one more caller and no new code.
 
 Rejected: routes under `/sessions/{id}/`. The session would be a detour to
-find the setup, and "browse this machine" from anywhere else would need a
+find the machine, and "browse this machine" from anywhere else would need a
 session to exist first.
 
 ### 2. One shell script per operation, over `Transport`, on both transports
@@ -68,7 +68,7 @@ Elsewhere the phone picks an **id** and the server resolves which file it
 names, so an enrolled token cannot become "read me an arbitrary file". The
 explorer's whole purpose is the path, so it takes one. Recorded in PLAN.md's
 Security section in these terms: the token already gates spawning a
-bypass-permissions agent in any directory on any machine a setup names, and
+bypass-permissions agent in any directory on any configured machine, and
 that agent can already read and write every file its user can. The explorer
 is a shorter path to authority the token already holds, not new authority.
 The import rule stands where it is, because there a path was unnecessary and
@@ -89,7 +89,7 @@ is. The phone never resolves `..` itself.
 
 ### 5. A read is capped and typed, and every state it can be in has a word
 
-`GET /setups/{id}/file` answers with one of `text` (content, size, mtime,
+`GET /machines/{id}/file` answers with one of `text` (content, size, mtime,
 sha256), `binary` (not UTF-8; size reported, nothing shown), `tooBig` (over
 `FILE_LIMIT`, 1 MiB; size reported so the reader knows what they are looking
 at), or the machine's own error.
@@ -102,7 +102,7 @@ what it is.
 
 ### 6. A write is conditional on what the reader saw
 
-`PUT /setups/{id}/file` carries the sha256 the read reported. The script
+`PUT /machines/{id}/file` carries the sha256 the read reported. The script
 compares it against the file as it is now and exits distinctly if it differs;
 the server answers **409**. Agents edit files while people read them; this is
 the common case, not the exotic one, and silently overwriting an agent's edit
@@ -123,9 +123,9 @@ precondition is fresh without a second read.
 
 ### 7. Create refuses to overwrite
 
-`POST /setups/{id}/file` runs under `set -C` (noclobber) and `: > "$1"`, so a
+`POST /machines/{id}/file` runs under `set -C` (noclobber) and `: > "$1"`, so a
 name that exists fails with the shell's own message rather than truncating
-somebody's file; `POST /setups/{id}/dir` is `mkdir --` with the same
+somebody's file; `POST /machines/{id}/dir` is `mkdir --` with the same
 property. The modal names one thing in the current directory and has a switch
 for "directory"; a created file opens straight into edit mode, because an
 empty file is not something to look at.
@@ -275,14 +275,14 @@ already are. **Moving it is where the no-coordinate-taps rule got enforced**
 ### 14. File links in a session open in the explorer
 
 A markdown destination that is an absolute path or a local `file:` URI opens that document in the
-session's explorer, on the session's setup. A trailing editor line and optional column are removed;
+session's explorer, on the session's machine. A trailing editor line and optional column are removed;
 the viewer opens the file but does not yet scroll to a line. Web links, relative links and `file:`
 URIs naming another host keep their ordinary external behaviour. The distinction is deliberately
 narrow: a relative link might be a web reference, and the phone must not silently reinterpret it as
 a path on another machine.
 
-The markdown link handler is provided around the session rather than taught about setups. That
-keeps the renderer reusable and makes the explorer's existing setup target the one navigation path.
+The markdown link handler is provided around the session rather than taught about machines. That
+keeps the renderer reusable and makes the explorer's existing machine target the one navigation path.
 
 ## HTTP surface