Document billing estimates in excloud CLI skill

skills/excloud-cli/SKILL.md

@@ -63,6 +63,7 @@ The skill does _not_ hard-code IDs, instance type names, image IDs, subnet IDs,
 - `exc compute subnet list` + `exc compute subnet get --id <id>` — check `DISABLE_IPV4_PUBLIC_IP`: subnets with this set cannot take `--allocate_public_ipv4=true` at create time.
 - `exc securitygroup list` + `exc securitygroup rule list --security_group_id <id>` + `exc securitygroup binding list --security_group_id <id>` (or `--interface_id <id>`) — confirm what a SG allows and where it's bound before relying on it.
 - `exc compute publicip list` / `exc compute key list` / `exc compute volume list` / `exc compute snapshot list` — authoritative inventories for each resource type.
+- `exc billing estimate --help` + `exc compute instancetype list` — shape a pre-flight monthly cost estimate before creating or scaling VMs. Instance type names and pricing inputs change; verify them rather than hard-coding.
 - `exc buckets list` / `exc buckets get <name>` / `exc buckets usage` — authoritative object-storage inventory and quota checks.
 - `exc buckets objects list <bucket> [--prefix <prefix>] [--all]` — discover keys before copy/delete/share operations.
 - `exc buckets keys list` and `exc buckets multipart list <bucket>` — discover S3 access keys and abandoned multipart uploads before managing them.
@@ -381,6 +382,33 @@ On a TTY, `reveal` also prints a stderr note "Revealed version N of secret M (au
 - `exc policy binding delete --policy_id <id> (--account_id <id> | --service_account_id <id>)`
 - `exc billing get` / `exc quota`
 
+### Billing estimates
+
+Use `exc billing estimate` for a read-only pre-flight monthly cost estimate before `compute create`, cluster worker sizing, or any conversation where the user is choosing between VM sizes. Always run `exc billing estimate --help` first; the command is generated and flags may shift.
+
+Typical shape:
+
+```bash
+exc billing estimate \
+  --instance_type <type> \
+  --count 1 \
+  --root_volume_gib 25 \
+  --baseline_iops 3000 \
+  --baseline_throughput_mbps 125 \
+  --monthly_egress_gib 0 \
+  --has_public_ipv4=false
+```
+
+Notes:
+
+- `--instance_type` is required; discover valid names with `exc compute instancetype list`.
+- `--count`, `--root_volume_gib`, `--baseline_iops`, `--baseline_throughput_mbps`, and `--monthly_egress_gib` are optional numeric inputs. Omitted or zero values let the service apply its defaults where supported; pass explicit values when mirroring a planned `compute create`.
+- `--monthly_egress_gib` is a floating-point flag, so decimal values are valid if the installed help shows it.
+- `--has_public_ipv4` is boolean; pass `--has_public_ipv4=true` when estimating a public IPv4 allocation.
+- The command uses the default zone from CLI config; there is normally no user-facing `--zone_id` flag in the generated command.
+- Output is a human-readable cost table with component rows (`Instance`, optional `Storage`, optional `Network`) and `TOTAL` / hourly summary rows. It is for display and comparison, not JSON scripting.
+- If the service has no price data for an instance type, the command prints `No pricing data found for instance type: <type>`.
+
 ## Config and misc
 
 - `exc me` / `exc version` / `exc completion <bash|zsh|fish|powershell>`
@@ -391,7 +419,7 @@ On a TTY, `reveal` also prints a stderr note "Revealed version N of secret M (au
 
 Every command either prints a column table (or TSV) or prints JSON — no command should print raw Go-struct dumps anymore. Both shapes are machine-parseable; pick your tool accordingly.
 
-- **Column tables / TSV** (awk / `cut` / `awk -F\t` friendly): `compute list`, `compute get`, `compute create`, `compute terminate` (TSV `vm_id\tstate`), `compute instancetype list` / `capacity`, `compute image list`, `compute subnet list`, `compute volume list`, `compute volume get`, `compute snapshot list`, `compute publicip list`, `compute key list`, `securitygroup list` / `rule list` / `binding list`, `org list`, `account list`, `apikey list`, `policy list`, `config list`, `compute seriallogs`, `buckets list`, `buckets ls`, `buckets objects list`, `buckets keys list`, `buckets multipart list`.
+- **Column tables / TSV** (awk / `cut` / `awk -F\t` friendly): `compute list`, `compute get`, `compute create`, `compute terminate` (TSV `vm_id\tstate`), `compute instancetype list` / `capacity`, `compute image list`, `compute subnet list`, `compute volume list`, `compute volume get`, `compute snapshot list`, `compute publicip list`, `compute key list`, `securitygroup list` / `rule list` / `binding list`, `org list`, `account list`, `apikey list`, `policy list`, `billing estimate`, `config list`, `compute seriallogs`, `buckets list`, `buckets ls`, `buckets objects list`, `buckets keys list`, `buckets multipart list`.
 - **JSON** (pipe through `jq`): `me`, `quota`, `billing get`, `compute health` (`{"raw":"OK"}`), `k8s health`, `compute subnet get`, `compute publicip get`, `compute key get`, `securitygroup get`, `compute metrics`, `compute connect`, `serviceaccount list`, `compute protect`, `compute unprotect`, `compute rename`, `k8s cluster kubeconfig get` (raw kubeconfig YAML, not JSON-wrapped), `buckets get`, `buckets usage`, `buckets keys create`, multipart create/uploadpart/complete/abort, and the inline `kubeconfig` field inside the JSON response from `k8s cluster create` when `-o` is not set.
 
 Many bucket list/delete commands have explicit `--json`; use it for scripts instead of scraping tables. `buckets objects presign` intentionally prints only the URL so it can be piped to tools like `pbcopy`.