skills: switch to directory-based resource scanning

[Quim Muntal (qmuntal)]

Port of microsoft/agent-framework#5078 and microsoft/agent-framework#5205.

Summary

Replace markdown-link-based resource extraction with directory-based scanning per the Agent Skills specification.

Changes

Resource discovery (loader.go)

• Directory-based scanning: Resources are now discovered by scanning configured directories non-recursively, filtered by extension. Replaces the previous approach of extracting resource paths from markdown links in the SKILL.md body.
• Default directories: references/ and assets/ (per the spec).
• Default extensions: .md, .json, .yaml, .yml, .csv, .xml, .txt.
• Root opt-in: Use "." in ResourceDirectories to scan the skill root; SKILL.md is always excluded.
• Path validation: Uses filepath.IsLocal to reject absolute paths and .. segments. Normalizes with filepath.Clean + filepath.ToSlash.
• Removed extractResourcePaths, validateResources, resourceLinkRegex.

Config (skills.go)

• Added Config.ResourceDirectories -- configurable directories (replaces defaults when set).
• Added Config.AllowedResourceExtensions -- configurable extensions (replaces defaults when set).
• Updated New() doc to recommend os.Root.FS over os.DirFS for symlink protection.

Example

• Updated 01_basic_skills to use os.OpenRoot().FS().

Tests

• 17 new/updated tests covering default directories, custom directories, root opt-in, extension filtering, non-recursive scanning, nested paths, SKILL.md exclusion, config validation, and deduplication.

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Updates skill resource discovery to match the Agent Skills spec by scanning configured directories (vs parsing markdown links), with configurable directories/extensions and updated examples/tests.

Changes:

• Replace markdown-link-based resource extraction with non-recursive directory scanning (references/, assets/ by default), including path normalization/validation.
• Add configuration for resource directories and allowed resource extensions.
• Update example to use os.OpenRoot().FS() and expand test coverage for discovery/config behaviors.

Show a summary per file

File	Description
memory/skills/loader.go	Implements directory-based resource discovery, config normalization/validation, and extension filtering.
memory/skills/skills.go	Wires new config fields into loader creation and updates New() guidance for safer FS usage.
memory/skills/skills_test.go	Updates existing tests and adds extensive new tests for directory/extension scanning behavior.
examples/skills/01_basic_skills/main.go	Switches example from os.DirFS to os.OpenRoot().FS() for symlink-escape hardening.

Copilot's findings

Tip

Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

• Files reviewed: 4/4 changed files
• Comments generated: 3