feat: flexible intake — deferred variables + prepared sessions (#103)

* feat: flexible intake — deferred variables + prepared sessions

Remove blocking intake form modal. Variables are now filled inline during
flow execution or pre-filled via prepared sessions. Adds PATCH /sessions/{id}/variables
endpoint, POST /sessions/prepare for session pre-staging, inline variable prompts
in StepDetail, editable Session Variables panel, and "Prepared for You" dashboard section.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: pass treeData directly to startSession to avoid stale state

setTree(treeData) hasn't committed when startSession runs immediately
after, so tree is still null and getStepsFromTree returns []. This
caused the step detail area to render empty on new session start.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* feat: wire PrepareSessionModal entry point in Flow Library

Add "Prepare session" button (clipboard icon) to grid, list, and table
views for procedural/maintenance flows. Clicking fetches tree intake
fields and account members, then opens PrepareSessionModal.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/components/procedural/ResolvedText.tsx

@@ -0,0 +1,87 @@
+import type { IntakeFormField } from '@/types'
+import { InlineVariablePrompt } from './InlineVariablePrompt'
+
+interface ResolvedTextProps {
+  text: string
+  variables: Record<string, string>
+  intakeFields?: IntakeFormField[]
+  onVariableSubmit?: (variableName: string, value: string) => void
+  className?: string
+}
+
+/**
+ * Renders text with resolved variables inline. Unresolved [VAR:x] tokens
+ * are replaced with interactive InlineVariablePrompt components.
+ */
+export function ResolvedText({
+  text,
+  variables,
+  intakeFields,
+  onVariableSubmit,
+  className,
+}: ResolvedTextProps) {
+  if (!text) return null
+
+  // Split on variable tokens, keeping the tokens in the result
+  const tokenPattern = /(\[(?:VAR|USER_INPUT):([^\]]+)\])/g
+  const parts: Array<{ type: 'text'; value: string } | { type: 'var'; variableName: string; token: string }> = []
+  let lastIndex = 0
+  let match
+
+  // Remove [SAVE_AS:...] tokens first
+  const cleaned = text.replace(/\[SAVE_AS:[^\]]+\]/g, '')
+
+  while ((match = tokenPattern.exec(cleaned)) !== null) {
+    // Add text before the token
+    if (match.index > lastIndex) {
+      parts.push({ type: 'text', value: cleaned.slice(lastIndex, match.index) })
+    }
+
+    const variableName = match[2].trim()
+    const resolvedValue = variables[variableName]
+
+    if (resolvedValue && resolvedValue.trim()) {
+      // Variable is resolved — render as plain text
+      parts.push({ type: 'text', value: resolvedValue })
+    } else {
+      // Variable is unresolved — render as inline prompt
+      parts.push({ type: 'var', variableName, token: match[1] })
+    }
+
+    lastIndex = match.index + match[0].length
+  }
+
+  // Add remaining text
+  if (lastIndex < cleaned.length) {
+    parts.push({ type: 'text', value: cleaned.slice(lastIndex) })
+  }
+
+  // If no unresolved variables, just render plain text
+  const hasUnresolved = parts.some(p => p.type === 'var')
+  if (!hasUnresolved) {
+    const fullText = parts.map(p => p.type === 'text' ? p.value : '').join('')
+    return <span className={className}>{fullText}</span>
+  }
+
+  // Find field metadata helper
+  const getFieldMeta = (varName: string) =>
+    intakeFields?.find(f => f.variable_name === varName)
+
+  return (
+    <span className={className}>
+      {parts.map((part, i) => {
+        if (part.type === 'text') {
+          return <span key={i}>{part.value}</span>
+        }
+        return (
+          <InlineVariablePrompt
+            key={`${part.variableName}-${i}`}
+            variableName={part.variableName}
+            fieldMeta={getFieldMeta(part.variableName)}
+            onSubmit={onVariableSubmit || (() => {})}
+          />
+        )
+      })}
+    </span>
+  )
+}