Problem

When a config schema has multiple autocomplete fields where one depends on another's value (e.g., selecting a Jira project first, then filtering issue types by that project), there's no way to pass the current value of one field as a query parameter to another field's autocomplete URL.

Currently, FormAutocomplete only passes the search term (q) as a query parameter. The URL is fully static.

Use Case

The Jira integration in flowdrop-rs has these config fields:

1. account - autocomplete selecting a Jira account secret
2. project - autocomplete listing projects (needs account to authenticate)
3. issue_type - autocomplete listing issue types (needs account + project)
4. assignee - autocomplete searching users (needs account + project)

The backend endpoints in flowdrop-rs are ready:

• GET /api/flowdrop/jira/projects?account={account}
• GET /api/flowdrop/jira/issue-types?account={account}&project={project}
• GET /api/flowdrop/jira/users?account={account}&project={project}&q={query}

But the frontend can't pass the selected account and project values to these URLs.

Proposed Solution

Add an optional params field to AutocompleteConfig:

interface AutocompleteConfig {
  url: string;
  // ... existing fields ...
  
  /** Map of URL query parameter names to config field names.
   *  When fetching autocomplete options, the current value of
   *  each referenced field is appended as a query parameter.
   *  
   *  Example: { "account": "account", "project": "project" }
   *  If the "account" field has value "my-jira", the fetch URL becomes:
   *  /api/flowdrop/jira/issue-types?account=my-jira&q=...
   */
  params?: Record<string, string>;
}

In FormAutocomplete, when building the fetch URL, iterate over params and append each mapped field's current value from the form state.

Bonus: Reactive refresh

When a dependency field value changes (e.g., user selects a different project), the dependent autocomplete should:

1. Clear its current value (since it may no longer be valid)
2. Refetch options on next focus

Backend Type (already in place)

The Rust AutocompleteConfig struct in flowdrop-rs would add:

pub params: Option<HashMap<String, String>>,

Context

This was identified during the implementation of Jira integration node types (flowdrop-rs 005-jira-node-types). The backend proxy endpoints and node config schemas are ready — only the frontend parameter passing is missing.