fix(pstack): make a brand with a type guard, not as

[poteto]

Why

The branded-type example in typescript-best-practices built its brand with return input as AgentId, which the skill's "No as casts" row tells agents to avoid. Agents copy the example, so it taught the cast the rules forbid.

What changed

• parseAgentId now narrows through an isAgentId type guard and returns the input with no cast.
• The "Branded types" row says a brand comes from a verifying type guard (input is AgentId), never from as.

Scope

• pstack/skills/typescript-best-practices and its regenerated Claude Code copy.
• Does not change the general cast rules, which still allow as after validation.

Blast Radius

Only the text agents read for TypeScript edits changes. No code, build, or runtime path changes.

Verification

• A strict TypeScript compile of the new example has no as and no errors. It still rejects a raw string where an AgentId is expected.
• node scripts/validate-plugins.mjs passes, and node scripts/generate-pstack-harness-trees.mjs --check reports the harness tree up to date.

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Note

Low Risk
Documentation-only changes to agent skill text; no application code, build, or runtime behavior.

Overview
Aligns the typescript-best-practices branded-type guidance with the skill’s own No as casts rule so agents don’t copy a forbidden pattern.

The Branded types table row now states that a brand must come from a verifying type guard (input is AgentId), not from as. The patterns.md example adds isAgentId, uses it in parseAgentId, and returns the narrowed string without a cast.

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