docs: fix PRD consistency and align all docs with SSH client-only (FR-006)

PRD fixes:
- Remove duplicate 'Installation Behavior' section
- Fix malformed terminology table (missing pipe separator)

Documentation alignment with FR-006:
- README.md: Change SSH/firewall to client-only, no inbound access
- TEST-COVERAGE.md: Remove 'Firewall allows SSH inbound'
- VERIFICATION-REPORT.md: Fix password config docs to match preseed.cfg
- COMPLIANCE.md: Change 'SSH Hardening' to 'SSH Client-Only'

Test enhancements:
- Expand unit tests for encryption, firewall, security hardening
- Add comprehensive coverage for FR-001 through FR-009 requirements

All changes ensure documentation and tests align with PRD.md FR-006
which requires SSH client-only with no server or inbound access.

💘 Generated with Crush

Assisted-by: GLM-4.7 via Crush <crush@charm.land>

tests/integration/e2e_test.bats

@@ -4,7 +4,7 @@
 @test "all documentation files exist" {
     [ -f "/workspace/AGENTS.md" ]
     [ -f "/workspace/README.md" ]
-    [ -f "/workspace/PRD.md" ]
+    [ -f "/workspace/docs/PRD.md" ]
 }
 
 @test "docs directory exists" {