build(snap): trim the description and part comments

The description carried a confinement section SPEC.md already owns,
and the part comments narrated build steps the commands state on
their own. First run now shows a plain run instead of the microVM
proof.

snap/snapcraft.yaml

@@ -9,32 +9,22 @@ description: |
   away. Persistence crosses an explicit `-v/--volume` share or it does not
   happen.
 
-  ## Confinement
-
-  The host process never mounts a filesystem and never creates or
-  enters a namespace, so the whole runtime runs inside snapd's
-  default-deny seccomp allowlist. Working KVM is required; there is
-  no software fallback.
-
   ## First run
 
   Connect the KVM interface (home and network connect on their own):
 
       sudo snap connect ecrou:kvm
 
-  Then prove the machine:
+  Then run a command in a microVM:
 
-      ecrou run alpine -- uname -a
+      ecrou run ubuntu -- uname -a
-
-  The guest kernel version differing from the host is the microVM
-  proof.
 
   ## Diagnostics
 
   `ecrou probe` reports what a run would find: KVM, libkrun, the
   cache directory.
 
-  ## Where things live
+  ## Configuration and cache
 
   - image cache: `~/snap/ecrou/common/cache/ecrou`
   - config: `~/snap/ecrou/common/config/ecrou.yaml`
@@ -65,8 +55,6 @@ parts:
     source: .
     rust-channel: "1.98.1"
     rust-path: [crates/ecrou-cli]
-    # aws-lc-sys (the rustls provider) drives cmake and perl at build
-    # time; the rust plugin already brings gcc, curl, git, pkg-config.
     build-packages: [cmake, perl]
     override-build: |
       craftctl default
@@ -93,25 +81,17 @@ parts:
     source-depth: 1
     rust-channel: "1.98.1"
     override-build: |
-      # Build only the libkrun package; the rest of the workspace is
-      # the feature-gated device crates, not needed for the eleven
-      # stable-ABI calls ecrou makes. `net` is TSI, the guest
-      # networking.
       cargo build --release -p libkrun --features net
-      # No distro the snap bases ship from publishes libkrun.so.1, so
-      # the soname layout is set up here the way `make install`
-      # would.
       install -Dm755 target/release/libkrun.so \
         "$CRAFT_PART_INSTALL/lib/libkrun.so.1.19.7"
       ln -s libkrun.so.1.19.7 "$CRAFT_PART_INSTALL/lib/libkrun.so.1"
 
   libkrunfw:
     plugin: nil
-    # libkrunfw5 ships only in the current series' universe today,
+    # libkrunfw5 ships only in stonking universe today,
     # not in any LTS base, so the .deb comes straight from the pool.
     # The library embeds its kernel and has no external symbols, so
-    # it runs on the base's older glibc. The generic amd64 build, not
+    # it runs on the base's older glibc.
-    # the amd64v3 flavor: the snap should not require AVX2.
     build-packages: [curl]
     override-pull: |
       curl -fL -o libkrunfw5.deb \