syncro: finalize deploy-agent (installer URL = per-client vaulted secret, MSI)

Decoded the Syncro RMM installer URL from 4 client samples:
base64(v1-{customer_id}-{A}-48753-{policy_folder_id}). 48753 = our account id (constant);
customer_id + policy_folder_id are API-readable; A is an unguessable per-client security token
NOT exposed anywhere in the API -> the URL is NOT constructible and must be harvested per client
and vaulted. Installer is an MSI -> deploy uses msiexec /qn /norestart.

deploy-agent now reads clients/<slug>/syncro-agent-installer (credentials.installer_url) from
the vault (cascades-tucson, grabb-durando, reliant, howard-test seeded) and pushes via GuruRMM.
Findings recorded in test-findings.md.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.claude/commands/syncro.md

@@ -741,46 +741,51 @@ curl -s "${BASE}/rmm_alerts?per_page=50&api_key=${API_KEY}" | tr -d '\000-\037'
 
 #### Agent Deployment (`/syncro deploy-agent`) — hybrid via GuruRMM
 
-Push the Syncro RMM agent to a machine. Syncro's API has **no** installer-download endpoint,
-so this is a **hybrid**: the per-policy-folder installer (which embeds the customer enrollment
-token) is obtained once from the Syncro GUI and vaulted; **GuruRMM (`/rmm`)** does the actual
-push (it runs PowerShell as SYSTEM on the endpoint). `/rmm diagnose` already *detects* a
-Syncro agent as a competitor-RMM check — this is the deploy half.
+Push the Syncro RMM agent to a machine. Syncro's API has **no** installer-download endpoint
+(verified: 0 of 116 paths), so this is a **hybrid**: the per-policy-folder installer URL is
+harvested once from the Syncro GUI and **vaulted**; **GuruRMM (`/rmm`)** does the push (runs as
+SYSTEM). `/rmm diagnose` already *detects* a Syncro agent — this is the deploy half.
 
-**Prerequisites (one-time per customer):**
-1. In Syncro: **Assets & RMM → Downloads** (or the target Policy Folder) → copy the
-   `SyncroSetup-<company>-<token>.exe` **download URL**. It is per-policy-folder — the token
-   binds the installed agent to that customer + policy. Do NOT reuse one customer's URL for
-   another.
-2. Vault it via the `vault` skill at `clients/<slug>/syncro-agent-installer.sops.yaml`
-   (`credentials.installer_url`). Never hardcode the token URL.
+**The installer URL is a per-client SECRET and is NOT constructible.** Decoded (2026-07-10):
+`https://rmm.syncromsp.com/dl/msi/<b64>` where `<b64>` = base64 of
+`v1-{customer_id}-{A}-48753-{policy_folder_id}`. `48753` is OUR account id (constant across all
+clients); `customer_id` and `policy_folder_id` are API-readable — but **`A` is an unguessable
+~1.8-billion per-client security token that appears nowhere in the API** (checked customer +
+policy-folder objects). So you cannot build the URL; it must be harvested per client. Note the
+link is an **MSI** (`/dl/msi/`) → silent install is `msiexec /qn`, not the `.exe --console` path.
+
+**Prerequisites (one-time per client):**
+1. In Syncro GUI: the client's Policy Folder → **Downloads** → copy the `.../dl/msi/<token>` URL.
+2. Vault it (it embeds the secret `A`): `bash .claude/skills/vault/scripts/vault-helper.sh new
+   clients/<slug>/syncro-agent-installer --kind generic --name "Syncro RMM Installer - <Client>"
+   --set installer_url=<URL> --set customer_id=<N> --set policy_folder_id=<N>`. Already vaulted:
+   `cascades-tucson`, `grabb-durando`, `reliant`, `howard-test`.
 
 **Deploy workflow:**
-1. Resolve the target host in GuruRMM (`/rmm` — resolve hostname → UUID; confirm `os_type`
-   is `windows` and it is `is_connected`). Confirm the customer↔host mapping with the user.
-2. Preview the exact install command + target, get explicit confirmation.
-3. Dispatch via GuruRMM (`command_type: powershell`, SYSTEM context). The agent installs
-   **silently by default**; `--console` runs it non-interactively and `--allow-force-reboot`
-   permits the reboot Syncro triggers if it must update .NET first:
+1. Read the URL: `bash .claude/scripts/vault.sh get-field clients/<slug>/syncro-agent-installer
+   credentials.installer_url`. If the client has no entry, STOP and have the URL harvested first.
+2. Resolve the target host in GuruRMM (`/rmm` — hostname → UUID; confirm `os_type` windows +
+   `is_connected`). Confirm the client↔host mapping with the user.
+3. Preview the exact command + target; get explicit confirmation. **deploy-agent is
+   outward-facing (installs software, may reboot) — always confirm first.**
+4. Dispatch via GuruRMM (`command_type: powershell`, SYSTEM). Download the MSI and install silent:
 
    ```powershell
-   $url = '<vaulted SyncroSetup URL>'
-   $exe = "$env:TEMP\SyncroSetup.exe"
-   Invoke-WebRequest -Uri $url -OutFile $exe -UseBasicParsing
-   Start-Process -FilePath $exe -ArgumentList '--console','--allow-force-reboot' -Wait
+   $url = '<vaulted installer_url>'
+   $msi = "$env:TEMP\SyncroSetup.msi"
+   Invoke-WebRequest -Uri $url -OutFile $msi -UseBasicParsing
+   Start-Process msiexec.exe -ArgumentList '/i',"`"$msi`"",'/qn','/norestart' -Wait
    ```
-   (Refs: Syncro deploy docs `docs.syncrosecure.com/agents-alerts-automations/deploy-an-endpoint`;
-   community "Command Line install".) `--allow-force-reboot` CAN reboot the endpoint — treat
-   deploy-agent as an outward-facing action: confirm reboot tolerance with the user first.
-4. **Verify** the agent enrolled: after ~2-3 min, either re-query GuruRMM output, or confirm
-   the new asset appears under the customer via `GET /customer_assets?customer_id=N&query=<host>`
-   and/or that "Syncro" shows in the endpoint's `installed_applications`.
-5. Bot alert (RMM write → `[RMM]`/`[DEPLOY]` routes to #dev-alerts; Syncro-side note to
-   #bot-alerts if an asset record was created).
+   (`.exe` variant, if a client's link is `/dl/exe/`: `Start-Process $exe -ArgumentList
+   '--console','--allow-force-reboot' -Wait`.)
+5. **Verify enrollment:** after ~2-3 min, confirm the new asset appears —
+   `GET /customer_assets?customer_id=N&query=<host>` — and/or "Syncro" shows in the endpoint's
+   `installed_applications`.
+6. Bot alert (RMM write → `[RMM]`/`[DEPLOY]` routes to #dev-alerts).
 
-**[VERIFY before first production use]** Confirm `--console --allow-force-reboot` against the
-current Syncro installer on one ACG-internal test machine before rolling to a customer — the
-switches are stable historically but the installer is versioned.
+**[VERIFY before first production use]** Confirm the `msiexec /qn /norestart` silent behavior on
+RMM-TEST-MACHINE (Howard Test) before rolling to a customer. Full detail:
+`.claude/standards/syncro/test-findings.md`.
 
 #### Customers