skills: add pkg/skills for skill discovery from OLLIE_SKILLS_PATH

Scans colon-separated OLLIE_SKILLS_PATH (default ~/.config/ollie/skills)
for directories containing SKILL.md with name/description front-matter.
Reads from disk on every call, no caching. Deduplicates by name.

mkfile

@@ -3,6 +3,7 @@ all:V: install
 install:V:
 	mkdir -p $HOME/.config/ollie/sandbox
 	mkdir -p $HOME/.config/ollie/prompts
+	mkdir -p $HOME/.config/ollie/skills
 	cp -rf agents $HOME/.config/ollie
 	cp -rf sandbox $HOME/.config/ollie
 	cp -rf prompts $HOME/.config/ollie

pkg/skills/skills.go

@@ -0,0 +1,107 @@
+// Package skills discovers and serves skill definitions from OLLIE_SKILLS_PATH.
+//
+// Skills are directories containing a SKILL.md file with YAML front-matter
+// (name, description). They are exposed as a flat namespace of <name>.md files.
+// OLLIE_SKILLS_PATH is colon-separated; the first occurrence of a name wins.
+package skills
+
+import (
+	"bufio"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+)
+
+// Meta holds parsed front-matter from a SKILL.md file.
+type Meta struct {
+	Name        string
+	Description string
+	Dir         string // directory containing SKILL.md
+}
+
+// DefaultDir returns the default skills directory.
+func DefaultDir() string {
+	home, _ := os.UserHomeDir()
+	return home + "/.config/ollie/skills"
+}
+
+// Dirs returns the skill directories from OLLIE_SKILLS_PATH,
+// falling back to DefaultDir if unset.
+func Dirs() []string {
+	if env := os.Getenv("OLLIE_SKILLS_PATH"); env != "" {
+		return strings.Split(env, ":")
+	}
+	return []string{DefaultDir()}
+}
+
+// List scans all skill directories and returns deduplicated metadata.
+// First occurrence by directory order wins on name collision.
+func List() []Meta {
+	seen := make(map[string]bool)
+	var skills []Meta
+	for _, dir := range Dirs() {
+		entries, err := os.ReadDir(dir)
+		if err != nil {
+			continue
+		}
+		for _, e := range entries {
+			if !e.IsDir() || seen[e.Name()] {
+				continue
+			}
+			skillDir := filepath.Join(dir, e.Name())
+			meta, err := parseFrontMatter(skillDir)
+			if err != nil {
+				continue
+			}
+			seen[meta.Name] = true
+			skills = append(skills, *meta)
+		}
+	}
+	sort.Slice(skills, func(i, j int) bool { return skills[i].Name < skills[j].Name })
+	return skills
+}
+
+// Read returns the SKILL.md content for the named skill.
+func Read(name string) ([]byte, error) {
+	for _, m := range List() {
+		if m.Name == name {
+			return os.ReadFile(filepath.Join(m.Dir, "SKILL.md"))
+		}
+	}
+	return nil, os.ErrNotExist
+}
+
+func parseFrontMatter(skillDir string) (*Meta, error) {
+	f, err := os.Open(filepath.Join(skillDir, "SKILL.md"))
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	meta := &Meta{Name: filepath.Base(skillDir), Dir: skillDir}
+	scanner := bufio.NewScanner(f)
+	inFM := false
+	for scanner.Scan() {
+		line := scanner.Text()
+		if line == "---" {
+			if !inFM {
+				inFM = true
+				continue
+			}
+			break
+		}
+		if !inFM {
+			continue
+		}
+		if v, ok := strings.CutPrefix(line, "name:"); ok {
+			meta.Name = strings.TrimSpace(v)
+		} else if v, ok := strings.CutPrefix(line, "description:"); ok {
+			meta.Description = strings.TrimSpace(v)
+		}
+	}
+	if meta.Name == "" || meta.Description == "" {
+		return nil, os.ErrNotExist
+	}
+	return meta, nil
+}