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-extract-rules.md

@@ -0,0 +1,68 @@
+---
+description: Mine business logic from legacy code into testable, human-readable rule specifications
+argument-hint: <system-dir> [module-pattern]
+---
+
+Extract the **business rules** embedded in `legacy/$1` into a structured,
+testable specification — the institutional knowledge that's currently locked
+in code and in the heads of engineers who are about to retire.
+
+Scope: if a module pattern was given (`$2`), focus there; otherwise cover the
+entire system. Either way, prioritize calculation, validation, eligibility,
+and state-transition logic over plumbing.
+
+## Method
+
+Spawn **three business-rules-extractor subagents in parallel**, each assigned
+a different lens. If `$2` is non-empty, include "focusing on files matching
+$2" in each prompt.
+
+1. **Calculations** — "Find every formula, rate, threshold, and computed value
+   in legacy/$1. For each: what does it compute, what are the inputs, what is
+   the exact formula/algorithm, where is it implemented (file:line), and what
+   edge cases does the code handle?"
+
+2. **Validations & eligibility** — "Find every business validation, eligibility
+   check, and guard condition in legacy/$1. For each: what is being checked,
+   what happens on pass/fail, where is it (file:line)?"
+
+3. **State & lifecycle** — "Find every status field, state machine, and
+   lifecycle transition in legacy/$1. For each entity: what states exist,
+   what triggers transitions, what side-effects fire?"
+
+## Synthesize
+
+Merge the three result sets. Deduplicate. For each distinct rule, write a
+**Rule Card** in this exact format:
+
+```
+### RULE-NNN: <plain-English name>
+**Category:** Calculation | Validation | Lifecycle | Policy
+**Source:** `path/to/file.ext:line-line`
+**Plain English:** One sentence a business analyst would recognize.
+**Specification:**
+  Given <precondition>
+  When  <trigger>
+  Then  <outcome>
+  [And  <additional outcome>]
+**Parameters:** <constants, rates, thresholds with their current values>
+**Edge cases handled:** <list>
+**Confidence:** High | Medium | Low — <why>
+```
+
+Write all rule cards to `analysis/$1/BUSINESS_RULES.md` with:
+- A summary table at top (ID, name, category, source, confidence)
+- Rule cards grouped by category
+- A final **"Rules requiring SME confirmation"** section listing every
+  Medium/Low confidence rule with the specific question a human needs to answer
+
+## Generate the DTO catalog
+
+As a companion, create `analysis/$1/DATA_OBJECTS.md` cataloging the core
+data transfer objects / records / entities: name, fields with types, which
+rules consume/produce them, source location.
+
+## Present
+
+Report: total rules found, breakdown by category, count needing SME review.
+Suggest: `glow -p analysis/$1/BUSINESS_RULES.md`