Implement Overwrite Patch XML (OPX) and migrate from existing XML.

[mnismt]

Description

Introduce OPX v1: A clean-room, original XML protocol for Overwrite

• Core ops: Create, patch, replace, remove, and move files with explicit elements and new literals.
• Simple schema, optional metadata, and occurrence handling for reliable generation and parsing.

Solve #1

Protocol Specification

• Top-level: One or more elements; optional wrapper is allowed.
• attributes:
  • Required: file, op
  • Optional: root (for multi-root workspaces)
• Paths: Prefer workspace‑relative; don’t reference outside the workspace.
• Literals: In /, content must be between full-line markers <<< and >>>. Auto-heals lone <, <<, >, >> to proper markers.

Operations

op	Meaning	Required children
new	Create file
patch	Search-and-replace region	,
replace	Replace entire file
remove	Delete file	none
move	Rename/move file

Notes:

• is optional for a short reason.
• may use occurrence="first|last|N" to pick a specific match.

Example

New file

<edit file="src/utils/strings.ts" op="new">
  <why>Create utility module</why>
  <put>
<<<
export function titleCase(s: string): string {
  return s.split(/\s+/).map(w => w ? w[0]!.toUpperCase() + w.slice(1) : w).join(' ')
}
>>>
  </put>
</edit>

Patch region

<edit file="src/api/users.ts" op="patch">
  <why>Add timeout and error logging</why>
  <find occurrence="first">
<<<
export async function fetchUser(id: string) {
  const res = await fetch(`/api/users/${id}`);
  if (!res.ok) throw new Error(`Request failed: ${res.status}`);
  return res.json();
}
>>>
  </find>
  <put>
<<<
async function withTimeout<T>(p: Promise<T>, ms = 10000): Promise<T> {
  const t = new Promise<never>((_, r) => setTimeout(() => r(new Error('Request timed out')), ms));
  return Promise.race([p, t]);
}

export async function fetchUser(id: string) {
  try {
    const res = await withTimeout(fetch(`/api/users/${id}`), 10000);
    if (!res.ok) throw new Error(`Request failed: ${res.status}`);
    return res.json();
  } catch (err) {
    console.error('[api] fetchUser error', err);
    throw err;
  }
}
>>>
  </put>
</edit>

Replace entire file

<edit file="src/config/index.ts" op="replace">
  <put>
<<<
export interface AppConfig {
  apiBaseUrl: string;
  enableTelemetry: boolean;
  maxConcurrentJobs: number;
}

export const config: AppConfig = {
  apiBaseUrl: process.env.API_BASE_URL || 'http://localhost:3000',
  enableTelemetry: process.env.TELEMETRY === '1',
  maxConcurrentJobs: Number(process.env.MAX_JOBS || 4),
};
>>>
  </put>
</edit>

Remove file

<edit file="tests/legacy/user-auth.spec.ts" op="remove" />

Move / rename file

<edit file="src/lib/flags.ts" op="move">
  <to file="src/lib/feature-flags.ts" />
</edit>