feat(sdk,cli,core,build): phase 1 of agent skills

Full Phase 1 for the new ai.skills primitive — SDK + CLI, no
backend. Developer-authored folders (SKILL.md + scripts/references/
assets) discovered at build time, bundled into the deploy image at
/app/.trigger/skills/{id}/, and auto-wired into streamText at
runtime via the loadSkill/readFile/bash tools.

Adds a time-utils example skill to the ai-chat reference: two bash
scripts (now.sh, add.sh) plus a timezones.txt cheat-sheet, wired
into the aiChat agent via chat.skills.set() in onChatStart and
onPreload. Exercises the full pipeline end-to-end.

Changeset: patch bump for @trigger.dev/sdk, @trigger.dev/core,
@trigger.dev/build, trigger.dev.

Author: ericallam

.changeset/chat-agent-skills-phase-1.md

@@ -0,0 +1,16 @@
+---
+"@trigger.dev/sdk": patch
+"@trigger.dev/core": patch
+"@trigger.dev/build": patch
+"trigger.dev": patch
+---
+
+Add agent skills — developer-authored folders (`SKILL.md` + scripts/references/assets) bundled into the deploy image automatically, discovered by the chat agent via progressive disclosure. Built on the [AI SDK cookbook pattern](https://ai-sdk.dev/cookbook/guides/agent-skills) — portable across providers.
+
+**New:**
+- `skills.define({ id, path })` registers a skill with the resource catalog; the Trigger.dev CLI bundles the folder into `/app/.trigger/skills/{id}/` automatically — no `trigger.config.ts` changes, no build extension.
+- `SkillHandle.local()` reads the bundled `SKILL.md` at runtime, parses frontmatter, returns a `ResolvedSkill`.
+- `chat.skills.set([...])` stores resolved skills for the current run.
+- `chat.toStreamTextOptions()` auto-injects the skills preamble into the system prompt and merges three tools — `loadSkill`, `readFile`, `bash` — scoped per-skill with path-traversal guards and output caps (64 KB stdout/stderr, 1 MB `readFile`). `bash` runs with `cwd` = skill directory; the turn's abort signal propagates.
+
+Phase 1 is SDK + CLI only — no backend, no dashboard overrides. Dashboard-editable `SKILL.md` text lands in Phase 2 (`skill.resolve()` currently throws).

references/ai-chat/src/trigger/chat.ts

@@ -1,5 +1,5 @@
 import { chat, type ChatTaskWirePayload } from "@trigger.dev/sdk/ai";
-import { logger, prompts } from "@trigger.dev/sdk";
+import { logger, prompts, skills } from "@trigger.dev/sdk";
 import {
   streamText,
   generateText,
@@ -89,6 +89,11 @@ When the user asks you to research a topic, use the deep research tool with rele
 - Keep responses under a few paragraphs unless the user asks for more.`,
 });
 
+const timeUtilsSkill = skills.define({
+  id: "time-utils",
+  path: "./skills/time-utils",
+});
+
 const selfReviewPrompt = prompts.define({
   id: "ai-chat-self-review",
   model: "openai:gpt-4o-mini" satisfies RegistryLanguageModelId,
@@ -274,6 +279,7 @@ export const aiChat = chat
         plan: user.plan as string,
       });
       chat.prompt.set(resolved);
+      chat.skills.set([await timeUtilsSkill.local()]);
 
       await prisma.chat.upsert({
         where: { id: chatId },
@@ -322,6 +328,7 @@ export const aiChat = chat
         plan: user.plan as string,
       });
       chat.prompt.set(resolved);
+      chat.skills.set([await timeUtilsSkill.local()]);
 
       if (!continuation) {
         await prisma.chat.upsert({

references/ai-chat/src/trigger/skills/time-utils/SKILL.md

@@ -0,0 +1,37 @@
+---
+name: time-utils
+description: Compute and format dates/times in arbitrary timezones using a small set of bundled bash scripts. Use when the user asks about "what time is it", "current time in <city>", date math, or timezone conversions.
+---
+
+# Time utilities
+
+This skill bundles small bash scripts that shell out to `date` for timezone-aware answers without the model having to reason about offsets.
+
+## When to use
+
+- The user asks for the current time in a specific timezone (e.g. "what time is it in Tokyo?")
+- The user wants a date formatted in a specific way
+- The user needs a relative time (e.g. "what's the date 3 days from now?")
+
+## Scripts
+
+### `scripts/now.sh [TZ]`
+
+Prints the current time in the given IANA timezone (default `UTC`). Example:
+
+```
+bash scripts/now.sh America/Los_Angeles
+```
+
+### `scripts/add.sh DAYS [TZ]`
+
+Prints a date `DAYS` days from now in the given timezone. `DAYS` can be negative. Example:
+
+```
+bash scripts/add.sh 3 Europe/London
+```
+
+## Tips
+
+- IANA timezone names only (`America/New_York`, not `EST`).
+- See `references/timezones.txt` for a short cheat-sheet of common zones.

references/ai-chat/src/trigger/skills/time-utils/references/timezones.txt

@@ -0,0 +1,30 @@
+Common IANA timezones:
+
+North America:
+  America/New_York       (US Eastern)
+  America/Chicago        (US Central)
+  America/Denver         (US Mountain)
+  America/Los_Angeles    (US Pacific)
+  America/Toronto
+  America/Mexico_City
+
+Europe:
+  Europe/London
+  Europe/Paris
+  Europe/Berlin
+  Europe/Amsterdam
+  Europe/Madrid
+  Europe/Dublin
+
+Asia & Pacific:
+  Asia/Tokyo
+  Asia/Shanghai
+  Asia/Singapore
+  Asia/Kolkata           (India, UTC+5:30)
+  Australia/Sydney
+  Pacific/Auckland
+
+Others:
+  UTC
+  America/Sao_Paulo
+  Africa/Johannesburg

references/ai-chat/src/trigger/skills/time-utils/scripts/add.sh

@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+set -euo pipefail
+DAYS="${1:?days argument required}"
+TZ="${2:-UTC}"
+TZ="$TZ" date -d "${DAYS} days" '+%Y-%m-%d %H:%M:%S %Z' 2>/dev/null \
+  || TZ="$TZ" date -v"${DAYS}d" '+%Y-%m-%d %H:%M:%S %Z'

references/ai-chat/src/trigger/skills/time-utils/scripts/now.sh

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+set -euo pipefail
+TZ="${1:-UTC}"
+TZ="$TZ" date -u '+%Y-%m-%d %H:%M:%S %Z' 2>/dev/null || TZ="$TZ" date '+%Y-%m-%d %H:%M:%S %Z'