Add code-modernization plugin

Structured workflow (assess → map → extract-rules → reimagine → transform →
harden) and specialist agents (legacy-analyst, business-rules-extractor,
architecture-critic, security-auditor, test-engineer) for modernizing legacy
codebases into current stacks.

plugins/code-modernization/commands/modernize-map.md

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+---
+description: Dependency & topology mapping — call graphs, data lineage, batch flows, rendered as navigable diagrams
+argument-hint: <system-dir>
+---
+
+Build a **dependency and topology map** of `legacy/$1` and render it visually.
+
+The assessment gave us domains. Now go one level deeper: how do the *pieces*
+connect? This is the map an engineer needs before touching anything.
+
+## What to produce
+
+Write a one-off analysis script (Python or shell — your choice) that parses
+the source under `legacy/$1` and extracts:
+
+- **Program/module call graph** — who calls whom (for COBOL: `CALL` statements
+  and CICS `LINK`/`XCTL`; for Java: class-level imports/invocations; for Node:
+  `require`/`import`)
+- **Data dependency graph** — which programs read/write which data stores
+  (COBOL: copybooks + VSAM/DB2 in JCL DD statements; Java: JPA entities/tables;
+  Node: model files)
+- **Entry points** — batch jobs, transaction IDs, HTTP routes, CLI commands
+- **Dead-end candidates** — modules with no inbound edges (potential dead code)
+
+Save the script as `analysis/$1/extract_topology.py` (or `.sh`) so it can be
+re-run and audited. Run it. Show the raw output.
+
+## Render
+
+From the extracted data, generate **three Mermaid diagrams** and write them
+to `analysis/$1/TOPOLOGY.html` so the artifact pane renders them live.
+
+The HTML page must use: dark `#1e1e1e` background, `#d4d4d4` text,
+`#cc785c` for `<h2>`/accents, `system-ui` font, all CSS **inline** (no
+external stylesheets). Each diagram goes in a
+`<pre class="mermaid">...</pre>` block — the artifact server loads
+mermaid.js and renders client-side. Do **not** wrap diagrams in
+markdown ` ``` ` fences inside the HTML.
+
+1. **`graph TD` — Module call graph.** Cluster by domain (use `subgraph`).
+   Highlight entry points in a distinct style. Cap at ~40 nodes — if larger,
+   show domain-level with one expanded domain.
+
+2. **`graph LR` — Data lineage.** Programs → data stores.
+   Mark read vs write edges.
+
+3. **`flowchart TD` — Critical path.** Trace ONE end-to-end business flow
+   (e.g., "monthly billing run" or "process payment") through every program
+   and data store it touches, in execution order. If the `observability`
+   MCP server is connected, annotate each batch step with its p50/p99
+   wall-clock from `get_batch_runtimes`.
+
+Also export the three diagrams as standalone `.mmd` files for re-use:
+`analysis/$1/call-graph.mmd`, `analysis/$1/data-lineage.mmd`,
+`analysis/$1/critical-path.mmd`.
+
+## Annotate
+
+Below each `<pre class="mermaid">` block in TOPOLOGY.html, add a `<ul>`
+with 3-5 **architect observations**: tight coupling clusters, single
+points of failure, candidates for service extraction, data stores
+touched by too many writers.
+
+## Present
+
+Tell the user to open `analysis/$1/TOPOLOGY.html` in the artifact pane.