ci(windows): make provision.ps1 self-sufficient (dedicated user, parser-bug fix); refresh stale workflow comments

.gitea/workflows/build-windows.yml

@@ -87,9 +87,10 @@ jobs:
       - name: Ensure Rust toolchain configured for runner user
         shell: pwsh
         run: |
-          # provision.ps1 ran rustup as an admin user; act_runner runs as LocalSystem
-          # which has its own (empty) $RUSTUP_HOME. Bootstrap the default toolchain
-          # for LocalSystem on first run -- subsequent runs are no-ops.
+          # provision.ps1 installs rust machine-wide (CARGO_HOME=C:\cargo,
+          # RUSTUP_HOME=C:\rustup) so this is normally a no-op verification.
+          # Kept as a guardrail in case the runner was provisioned with an
+          # older script or by hand.
           rustup --version
           rustup toolchain install $env:RUST_VERSION --profile minimal --component rustfmt
           if ($LASTEXITCODE -ne 0) { throw "rustup toolchain install failed ($LASTEXITCODE)" }
@@ -102,9 +103,9 @@ jobs:
       - name: Install flutter_rust_bridge codegen tools
         shell: pwsh
         run: |
-          # Pin the install destination with --root so we don't have to guess at
-          # the runner's $USERPROFILE (act_runner runs as LocalSystem on this host,
-          # which makes $USERPROFILE a non-obvious system path).
+          # Pin the install destination with --root so the resulting binaries land
+          # in a deterministic, machine-wide path regardless of which user the
+          # runner service is configured to run as.
           $tools = 'C:\cargo-tools'
           New-Item -ItemType Directory -Force -Path "$tools\bin" | Out-Null
 
@@ -257,14 +258,13 @@ jobs:
             fi
           fi
 
-      # The monolithic `python build.py` invocation that the upstream GitHub
-      # workflow uses runs cargo and `flutter build windows` back-to-back. On this
-      # self-hosted runner, *something* during the ~14min cargo build wipes out
-      # flutter/windows, which then makes the subsequent flutter build fail with
-      # "source directory does not exist" -- even though the diagnostic step
-      # immediately above confirms the dir is fully present at that moment.
-      # Splitting the build into discrete steps lets us restore flutter/windows
-      # right before flutter needs it, after cargo has finished.
+      # The upstream GitHub workflow runs `python build.py` which chains cargo +
+      # `flutter build windows` in one step. We split that here so we can:
+      #   - get a checkpoint between cargo and flutter (~14 min apart)
+      #   - restore flutter/windows from git index if anything has clobbered it
+      #     (early in our self-hosted bring-up, flutter/windows occasionally
+      #     vanished during the cargo phase under LocalSystem; the restore is
+      #     defensive and a no-op once the runner is on a normal user)
 
       - name: Cargo build (virtual_display dylib + main lib)
         shell: pwsh
@@ -282,10 +282,9 @@ jobs:
             throw "target\release\librustdesk.dll missing after cargo build"
           }
 
-      # Restore + build are intentionally one step. flutter/windows has been
-      # observed to disappear between steps on this runner (cause unidentified --
-      # likely Windows Defender quarantine, possibly act_runner workspace handling).
-      # Keeping them atomic eliminates any window of opportunity for that to happen.
+      # Restore + build are intentionally one step. Closes any potential window
+      # for flutter/windows to vanish between a separate restore step and the
+      # build, regardless of root cause.
       - name: Flutter build windows (with last-second restore)
         shell: pwsh
         run: |