Workflow template variables render literally in send_message despite inputs: declaration + --inputs JSON

[Svpplements]

Describe the bug

Workflow template variables ({{gate_name}}, {{gate_description}}) render as literal strings in send_message step output. The workflow engine does not interpolate {{variable}} references, regardless of whether inputs are declared in the workflow YAML and/or passed via buzz workflows trigger --inputs '<json>'.

Steps to reproduce

1. Create a workflow with template variables

name: trent-gate-approval
description: Replaces trent-gate-pusher 60s poller.
trigger:
  on: webhook
inputs:
  - key: gate_name
    required: true
  - key: gate_description
    required: true
steps:
  - id: gate_notification
    action: send_message
    text: "Gate approval required: {{gate_name}} - {{gate_description}}"
  - id: trent_approval
    action: request_approval
    from: <trent-pubkey-hex>
    message: "Approve gate: {{gate_name}}"
  - id: result
    action: send_message
    text: "Gate {{gate_name}} resolved by Trent."

Workflow ID: 2524dcb8-b67d-4146-9514-0d0303a75503
Channel: #command-center (fd688946-bf0e-4a70-bc9d-f51bd19736aa)
Relay: wss://suppvault.communities.buzz.xyz

2. Trigger it with inputs

buzz workflows trigger \
  --workflow 2524dcb8-b67d-4146-9514-0d0303a75503 \
  --inputs '{"gate_name":"INTERPOLATION-TEST","gate_description":"Testing if explicit inputs declaration fixes template interpolation"}'

3. Observe the message that lands in-channel

The send_message step posts: Gate approval required: {{gate_name}} - {{gate_description}}

The template variables are not replaced with the input values.

Expected behavior

send_message should post: Gate approval required: INTERPOLATION-TEST - Testing if explicit inputs declaration fixes template interpolation

At minimum, simple {{key}} substitution from --inputs JSON should work. Full mustache conditionals ({{#key}}...{{/key}}) are nice-to-have, not blocking.

Version and platform

• Buzz version: Desktop 0.5.5
• Relay: wss://suppvault.communities.buzz.xyz
• OS: macOS 26.5.2

Logs / additional context

4 trigger attempts — all show literal template vars

Run	Event ID	Content (verbatim)
1	3bb2dd19...	Gate approval required: {{gate_name}} - {{gate_description}}
2	d667d286...	Gate approval required: {{gate_name}} - {{gate_description}}
3	dcc841ba...	Gate approval required: {{gate_name}} - {{gate_description}}
4 (post-update)	a5ea5fec...	Gate approval required: {{gate_name}} - {{gate_description}}

All confirmed via buzz messages get --channel <UUID> --limit N.

What was tested to rule out user error

1. Without explicit inputs: declaration — same result (literal template vars)
2. With explicit inputs: declaration in workflow YAML (added inputs: block with key/required fields) — same result after workflow update
3. JSON input format — --inputs receives valid JSON with keys matching template var names
4. Direct buzz messages send — works correctly (pre-formatted message arrives as written), confirming the issue is specific to the workflow send_message step, not the message pipeline

Separate from request_approval defect

This is independent of the request_approval silent-no-op bug (filed separately). Template interpolation affects send_message text even in workflows that don't use request_approval.