docs: describe Flox in our own voice, not a third party's

Several passages described Flox the way an outsider describes another
company's product: "the flox packages ship their own Nix", "flox brings
its own Nix". We maintain Flox, so the possessive framing is wrong. The
distinction is between "ships their own Nix", which is what an observer
writes, and "ships with Nix", which is what the maintainer writes.

Most of these are prose, but one is not. The string in `core.warning`
that fires when reinstalling from a reference with no version ordering
is printed into the user's job log, and the `version` input description
in `action.yml` appears in the Marketplace listing. The README passages
render on the repository page. The remaining three are comments that no
user sees, corrected for consistency.

That warning also opened with a sentence fragment, and "afterwards" is
now "afterward".

Nothing behavioral changes. `dist/index.js` is regenerated because these
strings live in the bundle.

Author: brendaneamon

README.md

@@ -134,9 +134,9 @@ GitHub-hosted runners start every job on a fresh machine. Self-hosted runners, a
 
 **The runner needs `sudo` and `xz` present first.** Both are pre-dependencies of the flox `deb` and `rpm`, and `sudo` is needed regardless of how flox is installed, since this action uses it to write the Nix configuration. GitHub's hosted images carry both; a minimal self-hosted machine may not, in which case installation fails on the missing dependency and retries until it gives up. Install them as part of provisioning the runner.
 
-**It looks for flox before it looks for Nix.** The flox packages ship their own Nix and symlink it into `/usr/bin`, so a runner that has already installed flox has a `nix` on `PATH` that this action put there. Checking for `flox` first tells the two situations apart. When flox is already present the installation is skipped, `flox-preinstalled` is set to `true`, and the run costs nothing beyond the configuration steps. Set `force-reinstall: true` to install the channel's current release on every run instead, or pin `version` to reinstall whenever the pinned version is newer than the one already installed.
+**It looks for flox before it looks for Nix.** Installing flox also installs Nix, symlinked into `/usr/bin`, so a runner that has already installed flox has a `nix` on `PATH` that this action put there. Checking for `flox` first tells the two situations apart. When flox is already present the installation is skipped, `flox-preinstalled` is set to `true`, and the run costs nothing beyond the configuration steps. Set `force-reinstall: true` to install the channel's current release on every run instead, or pin `version` to reinstall whenever the pinned version is newer than the one already installed.
 
-**Downgrading in place fails with an error.** Flox brings its own Nix, and a Nix store cannot be read by a Nix older than the one that last wrote it, so installing an older flox over a newer one leaves a machine that breaks at first use rather than at install time. No package manager refuses the swap on those grounds, so the action checks before installing and stops. To move a runner back to an older version, remove flox and `/nix` from it and install again. A reference with no version ordering, a commit-hash channel for instance, cannot be checked this way; those are allowed through with a warning.
+**Downgrading in place fails with an error.** Flox ships with Nix, and a Nix store cannot be read by a Nix older than the one that last wrote it, so installing an older flox over a newer one leaves a machine that breaks at first use rather than at install time. No package manager refuses the swap on those grounds, so the action checks before installing and stops. To move a runner back to an older version, remove flox and `/nix` from it and install again. A reference with no version ordering, a commit-hash channel for instance, cannot be checked this way; those are allowed through with a warning.
 
 **It writes its Nix configuration fresh for every job.** The action writes its settings to a file under `/etc/nix/` named for the job that owns them, `install-flox-action-<run>-<attempt>-<id>.conf`, and adds one matching `!include` line to `/etc/nix/nix.conf`. A new file each job means the recorded `github-token` is never the expired one from a previous job, and it means a machine running several jobs at once gives each its own file: a shared one would let the first job to finish delete a token another job is still using. The post step removes this job's file and, with it, any include line whose file is gone, so a job killed before its post step ran does not leave litter behind. A stale token is worse than no token: Nix falls back to anonymous, rate-limited access when none is configured, but fails outright with `HTTP error 401` when it finds one that has expired.
 

action.yml

@@ -12,8 +12,8 @@ inputs:
     description: >-
       Select a specific version from a channel. Installing a
       version older than the one already on the runner fails:
-      flox brings its own Nix, which cannot read a store
-      written by a newer one.
+      flox ships with Nix, which cannot read a store written
+      by a newer one.
     default: ""
 
   channel:

dist/index.js

@@ -362,10 +362,10 @@ async function run() {
 
     core.startGroup('Download & Install flox')
 
-    // The flox packages symlink their own Nix into /usr/bin, so on a runner
-    // whose disk survives the job, `nix` alone cannot tell a Nix the user
-    // brought from the one an earlier run of this action installed. Asking
-    // for flox first answers the question directly.
+    // Installing flox also installs Nix, symlinked into /usr/bin, so on a
+    // runner whose disk survives the job, `nix` alone cannot tell a Nix the
+    // user brought from the one an earlier run of this action installed.
+    // Asking for flox first answers the question directly.
     const floxPath = await which('flox', { nothrow: true })
     const nix = await which('nix', { nothrow: true })
     const nixDetected = nix !== null
@@ -377,7 +377,7 @@ async function run() {
     if (floxPath !== null) {
       installedVersion = await getInstalledVersion()
 
-      // Flox brings its own Nix, and a Nix store database migrates only
+      // Flox ships with Nix, and a Nix store database migrates only
       // forward: a Nix older than the one that last wrote the store can refuse
       // to operate against it. No package manager declines the swap on those
       // grounds, so the install would succeed and the machine would break
@@ -404,12 +404,12 @@ async function run() {
         !isOrderable(requestedVersion, installedVersion)
       ) {
         core.warning(
-          'Reinstalling flox over an existing installation from a reference ' +
-            'with no version ordering, so this may be a downgrade. Downgrading ' +
-            'in place is not supported: flox brings its own Nix, and a Nix ' +
-            'store cannot be read by a Nix older than the one that last wrote ' +
-            'it. If anything fails against /nix afterwards, remove flox and ' +
-            '/nix from the runner and install again.'
+          'This reinstalls flox over an existing installation from a ' +
+            'reference with no version ordering, so it may be a downgrade. ' +
+            'Downgrading in place is not supported: flox ships with Nix, ' +
+            'and a Nix store cannot be read by a Nix older than the one ' +
+            'that last wrote it. If anything fails against /nix afterward, ' +
+            'remove flox and /nix from the runner and install again.'
         )
       }
     }

src/main.js

@@ -103,10 +103,10 @@ describe('main', () => {
       expect(core.setOutput).toHaveBeenCalledWith('nix-detected', 'true')
     })
 
-    // Issue #191: the flox packages symlink their own nix into /usr/bin, so a
+    // Issue #191: installing flox also installs nix into /usr/bin, so a
     // second run on a runner with a persistent disk finds a nix that this
     // action installed and mistakes it for one the user brought.
-    it('skips installation when flox is already present alongside its own nix', async () => {
+    it('skips installation when flox is already present alongside the nix it installed', async () => {
       mockWhich({ nix: '/usr/bin/nix', flox: '/usr/bin/flox' })
       core.getInput.mockImplementation(name => {
         if (name === 'channel') return 'stable'