[WM-BW-4] Control tailoring captures no justification rationale (SP 800-53B requirement)

## WM-BW-4 — No Tailoring Justification Rationale Captured

**Category:** Broken ATO/RMF Workflow | **Priority:** High
**Regulation:** SP 800-53B

### Observation
The SELECT phase has a baseline picker but no tailoring record model. SP 800-53B requires documented rationale for every add, remove, modify, and compensating control decision. No such record structure was observed.

### Evidence
- SELECT phase has baseline picker with no tailoring record model observed
- Issues #630, #551 — baseline selection path itself is broken

### Impact
Any control tailoring decisions made are undocumented and undefensible. An AO reviewing the SSP will have no rationale trail for non-baseline controls.

### Acceptance Criteria
- [ ] Tailoring record model implemented: stores action (add/remove/modify/compensating), control ID, rationale text, author, timestamp
- [ ] UI requires rationale entry before any tailoring decision is saved
- [ ] Tailoring justifications included in SSP export
- [ ] Fix baseline selection path (ref #630, #551)