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/factory.ts

@@ -0,0 +1,62 @@
+import type { HostConfig } from '../scripts/host-config';
+
+const factory: HostConfig = {
+  name: 'factory',
+  displayName: 'Factory Droid',
+  cliCommand: 'droid',
+  cliAliases: ['droid'],
+
+  globalRoot: '.factory/skills/gstack',
+  localSkillRoot: '.factory/skills/gstack',
+  hostSubdir: '.factory',
+  usesEnvVars: true,
+
+  frontmatter: {
+    mode: 'allowlist',
+    keepFields: ['name', 'description', 'user-invocable'],
+    descriptionLimit: null,
+    extraFields: {
+      'user-invocable': true,
+    },
+    conditionalFields: [
+      { if: { sensitive: true }, add: { 'disable-model-invocation': true } },
+    ],
+  },
+
+  generation: {
+    generateMetadata: false,
+    skipSkills: [],
+  },
+
+  pathRewrites: [
+    { from: '~/.claude/skills/gstack', to: '$GSTACK_ROOT' },
+    { from: '.claude/skills/gstack', to: '.factory/skills/gstack' },
+    { from: '.claude/skills/review', to: '.factory/skills/gstack/review' },
+    { from: '.claude/skills', to: '.factory/skills' },
+  ],
+  toolRewrites: {
+    'use the Bash tool': 'run this command',
+    'use the Write tool': 'create this file',
+    'use the Read tool': 'read the file',
+    'use the Agent tool': 'dispatch a subagent',
+    'use the Grep tool': 'search for',
+    'use the Glob tool': 'find files matching',
+  },
+
+  runtimeRoot: {
+    globalSymlinks: ['bin', 'browse/dist', 'browse/bin', 'gstack-upgrade', 'ETHOS.md'],
+    globalFiles: {
+      'review': ['checklist.md', 'TODOS-format.md'],
+    },
+  },
+
+  install: {
+    prefixable: false,
+    linkingStrategy: 'symlink-generated',
+  },
+
+  coAuthorTrailer: 'Co-Authored-By: Factory Droid <droid@users.noreply.github.com>',
+  learningsMode: 'full',
+};
+
+export default factory;