client: set disabled core speed to 0

[schmichael]

Workaround TotalCompute including compute from disabled cores by setting their speed to 0. This makes TotalCompute == UsableCompute with TotalCompute surprisingly being the number used by the scheduler.

---

Linux arm64 w/ 18 cores, 9 reservable

Before

Allocated Resources
CPU          Memory      Disk        Alloc Count
0/36000 MHz  0 B/16 GiB  0 B/12 GiB  0

    ^-- note how the denominator is **totalcompute** not usablecompute

Attributes
cpu.arch                                 = arm64
cpu.frequency                            = 2000
cpu.numcores                             = 18
cpu.reservablecores                      = 9
cpu.totalcompute                         = 36000
cpu.usablecompute                        = 18000

After

Allocated Resources
CPU          Memory      Disk        Alloc Count
0/18000 MHz  0 B/16 GiB  0 B/12 GiB  0

    ^-- total & usable compute match! --v

Attributes
cpu.arch                                 = arm64
cpu.numcores                             = 18
cpu.reservablecores                      = 9
cpu.totalcompute                         = 18000
cpu.usablecompute                        = 18000

After running 1 job with cpu=1000:

Allocated Resources
CPU             Memory          Disk            Alloc Count
1000/18000 MHz  256 MiB/16 GiB  300 MiB/12 GiB  1

   ^-- nothing new here

After adding another job with cores=2:

Allocated Resources
CPU             Memory          Disk            Alloc Count
5000/18000 MHz  512 MiB/16 GiB  600 MiB/12 GiB  2

  ^-- (2cores * 2000) + 1000cpu from previous job = 5000

Running as many jobs with cores=1 as possible:

nomad job run example-1core.nomad.hcl
...
    2026-10-16T12:08:07-07:00: Task Group "batchcore" (failed to place 991 allocations):
      * Resources exhausted on 1 nodes
      * Dimension "cores" exhausted on 1 nodes
    2026-10-16T12:08:07-07:00: Evaluation "a739ea00" waiting for additional capacity to place remainder

nomad node status -self -verbose
...
Allocated Resources
CPU              Memory          Disk            Alloc Count
18000/18000 MHz  900 MiB/16 GiB  2.6 GiB/12 GiB  9

   ^-- cpu and cores/allocs maxed as expected  --^

[schmichael]

Let's do #18