hermes host: generated skills reference nested gstack/<sub>/ paths that don't exist (prefix mode mismatch)

## Summary

When generating skills with `bun run gen:skill-docs --host hermes` on v1.3.0.0, the path rewrite rule

```ts
{ from: '~/.claude/skills/gstack', to: '~/.hermes/skills/gstack' }
```

in `hosts/hermes.ts` produces references to **nested** sub-skill paths under `~/.hermes/skills/gstack/<sub>/`, but Hermes install is prefix-mode (`gstack-/` flat), so those files never resolve. This also surfaces a second gap: several sub-skill reference files (`dx-hall-of-fame.md`, `vendor/pretext.js`, etc.) aren't installed on Hermes at all because `runtimeRoot.globalFiles` only lists `review/{checklist.md,TODOS-format.md}`.</sub>

## Repro

```sh
cd ~/.gstack/repos/gstack && git checkout v1.3.0.0
bun install && bun run gen:skill-docs --host hermes
grep -n "~/.hermes/skills/gstack/" .hermes/skills/gstack-autoplan/SKILL.md
```

Output includes:
```
.hermes/skills/gstack-autoplan/SKILL.md:1073:- ~/.hermes/skills/gstack/plan-ceo-review/SKILL.md
.hermes/skills/gstack-autoplan/SKILL.md:1074:- ~/.hermes/skills/gstack/plan-design-review/SKILL.md
.hermes/skills/gstack-autoplan/SKILL.md:1075:- ~/.hermes/skills/gstack/plan-eng-review/SKILL.md
.hermes/skills/gstack-autoplan/SKILL.md:1076:- ~/.hermes/skills/gstack/plan-devex-review/SKILL.md
```

None of these paths exist on a Hermes install — actual files are at `~/.hermes/skills/gstack-plan-ceo-review/SKILL.md` etc.

## Affected generated skills

| Skill | Broken ref | Fix |
|---|---|---|
| `gstack-autoplan` | Lines 1073–1076: `gstack/plan-{ceo,design,eng,devex}-review/SKILL.md` | Should be `gstack-plan-*-review/SKILL.md` |
| `gstack-plan-devex-review` | 9 refs to `gstack/plan-devex-review/dx-hall-of-fame.md` | File not installed on Hermes; needs globalFiles entry |
| `gstack-design-html` | `gstack/design-html/vendor/pretext.js` | Same — not installed on Hermes |
| `gstack-land-and-deploy` | `gstack/review/checklist.md` | ✅ Works (already in globalFiles) |

## Suggested fix

Two options:

1. **Path rewrite fix:** Add a rule for prefix mode that rewrites `~/.claude/skills/gstack/<sub>/` → `~/.hermes/skills/gstack-/` when the target host uses `install.prefixable: false` with flat namespace.</sub>

2. **Install reference files:** Expand `hosts/hermes.ts` `runtimeRoot.globalFiles` (or add `globalSymlinks` for sub-skill dirs) so `plan-devex-review/dx-hall-of-fame.md`, `design-html/vendor/pretext.js`, etc. get installed too.

Probably both — (1) for SKILL.md cross-references, (2) for non-SKILL asset files.

## Environment

- gstack: `v1.3.0.0`
- host: hermes (`./setup --host hermes` → falls through to `bun run gen:skill-docs --host hermes`)
- Hermes home: `~/.hermes/skills/`