feat: implement --with/--without selective install flags (#679)

Add agent: and skill: component families to the install component
catalog, enabling fine-grained selective install via CLI flags:

  ecc install --profile developer --with lang:typescript --without capability:orchestration
  ecc install --with lang:python --with agent:security-reviewer

Changes:
- Add agent: family (9 entries) and skill: family (10 entries) to
  manifests/install-components.json for granular component addressing
- Update install-components.schema.json to accept agent: and skill:
  family prefixes
- Register agent and skill family prefixes in COMPONENT_FAMILY_PREFIXES
  (scripts/lib/install-manifests.js)
- Add 41 comprehensive tests covering CLI parsing, request normalization,
  component catalog validation, plan resolution, target filtering,
  error handling, and end-to-end install with --with/--without flags

Closes #470

schemas/install-components.schema.json

@@ -26,7 +26,7 @@
         "properties": {
           "id": {
             "type": "string",
-            "pattern": "^(baseline|lang|framework|capability):[a-z0-9-]+$"
+            "pattern": "^(baseline|lang|framework|capability|agent|skill):[a-z0-9-]+$"
           },
           "family": {
             "type": "string",
@@ -34,7 +34,9 @@
               "baseline",
               "language",
               "framework",
-              "capability"
+              "capability",
+              "agent",
+              "skill"
             ]
           },
           "description": {