OpenClaw hook transform path containment missed symlink-resolved escapes

## Vulnerability

Webhook transform modules were validated with lexical path checks only. A symlink under the allowed hooks transform tree could resolve outside the intended directory and be dynamically imported.

## Affected Packages / Versions

- Package: `openclaw` (npm)
- Affected versions: `<= 2026.2.21-2`
- Patched version (planned next release): `2026.2.22`

## Impact

When an attacker can cause a transform module path to reference a symlinked entry that resolves outside the trusted transform directory, the gateway may import and execute unintended JavaScript with gateway-process privileges.

## Attack Preconditions

- Hook transforms are enabled and reachable.
- Attacker can influence transform path resolution (for example via privileged config access and/or writable filesystem path in the transform tree).
- A symlink escape exists to attacker-controlled code.

## Remediation

- Enforce realpath-aware containment for existing path ancestors before dynamic import.
- Keep lexical containment checks for traversal and absolute-path escapes.
- Add regression coverage for:
- transform module symlink escape rejection,
- `hooks.transformsDir` symlink escape rejection,
- in-root symlink allow-case.

## Fix Commit(s)

- `f4dd0577b055f77af783105bd65eae32f3d5e6a1`

OpenClaw thanks @aether-ai-agent for reporting.