Refactor documentation structure and improve validation checks; update VM state handling and error management.

DEVELOPER.md

@@ -58,7 +58,8 @@ Packet integration tests must remain inside disposable isolated namespaces.
 ```text
 ./
 ├── DEVELOPER.md              # This document
-├── README.md                 # Operator-facing usage guide
+├── README.md                 # Project overview
+├── USAGE.md                  # Operator command/deployment guide
 ├── pyproject.toml            # Package metadata and dependencies
 ├── uvm.py                    # Executable source-tree launcher
 ├── uvm/
@@ -345,12 +346,12 @@ processes, and allocation reuse.
 
 ### Start and Restart
 
-Start requires managed ports, a proven-gone process (or an already identified
-running VM), a complete safe private disk, and compatible retained gateway,
-network, and bridge settings. It verifies the VMM and installed **kernel**;
-the original rootfs template is not needed. It never recopies the rootfs,
-reprovisions credentials, or regenerates guest SSH host keys. Name/IP/MAC,
-ports, and guest disk changes survive stop/start; guest RAM does not.
+To boot a stopped/proven-gone VM, start requires managed ports, a complete safe
+private disk, and compatible retained gateway, network, and bridge settings.
+It verifies the VMM and installed **kernel**; the original rootfs template is
+not needed. It never recopies the rootfs, reprovisions credentials, or
+regenerates guest SSH host keys. Name/IP/MAC, ports, and guest disk changes
+survive stop/start; guest RAM does not.
 
 Start on a healthy running VM synchronizes policy without spawning another
 VMM. An ambiguous process or interrupted live boot/stop is not adopted as a
@@ -779,6 +780,7 @@ The packet test skipped in this workspace because namespace creation was
 denied (`Operation not permitted`). Document that permission limitation, not
 an assertion that real packets or a real host were validated. Unit tests and
 nft JSON parser checks are not substitutes for kernel packet-path execution.
+
 ### Isolated Host Validation
 
 No current test automatically boots a real microVM. Before a release, validate
@@ -841,7 +843,7 @@ The code is intentionally honest about current limits:
 - Firecracker is launched directly, even though the Jailer binary is
   downloaded.
 - No cgroup CPU, memory, I/O, or process limits are applied.
-- Fractional CPU is represented by rounding vCPUs up and printing an advisory.
+- Fractional CPU requests round vCPUs up without host quota enforcement.
 - Guest health is inferred from VMM process state, not application readiness.
 - No quotas, DHCP, host-port mapping, UDP/IPv6 services, or network tenancy.
 - No guest snapshots, extra disks, production image builder, or SSH-key injection.