feat: add typed host configs for Claude, Codex, Factory, and Kiro

Extract all hardcoded host-specific values from gen-skill-docs.ts,
types.ts, preamble.ts, review.ts, and setup into typed HostConfig
objects. Each host is a single file in hosts/ with its paths, frontmatter
rules, path/tool rewrites, runtime root manifest, and install behavior.

hosts/index.ts exports all configs, derives the Host type, and provides
resolveHostArg() for CLI alias handling (e.g., 'agents' -> 'codex',
'droid' -> 'factory').

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

hosts/claude.ts

@@ -0,0 +1,45 @@
+import type { HostConfig } from '../scripts/host-config';
+
+const claude: HostConfig = {
+  name: 'claude',
+  displayName: 'Claude Code',
+  cliCommand: 'claude',
+  cliAliases: [],
+
+  globalRoot: '.claude/skills/gstack',
+  localSkillRoot: '.claude/skills/gstack',
+  hostSubdir: '.claude',
+  usesEnvVars: false,
+
+  frontmatter: {
+    mode: 'denylist',
+    stripFields: ['sensitive', 'voice-triggers'],
+    descriptionLimit: null,
+  },
+
+  generation: {
+    generateMetadata: false,
+    skipSkills: [],
+  },
+
+  pathRewrites: [],  // Claude is the primary host — no rewrites needed
+  toolRewrites: {},
+  suppressedResolvers: [],
+
+  runtimeRoot: {
+    globalSymlinks: ['bin', 'browse/dist', 'browse/bin', 'gstack-upgrade', 'ETHOS.md'],
+    globalFiles: {
+      'review': ['checklist.md', 'TODOS-format.md'],
+    },
+  },
+
+  install: {
+    prefixable: true,
+    linkingStrategy: 'real-dir-symlink',
+  },
+
+  coAuthorTrailer: 'Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>',
+  learningsMode: 'full',
+};
+
+export default claude;