feat: cover pi and opencode in the home-manager module

They have no @file imports, so the module concatenates the shared
claude-md fragments into one AGENTS.md per tool (.pi/agent/ and
.config/opencode/), and links commands/ into opencode's commands dir.
Skills need nothing: pi reads ~/.agents/skills and opencode auto-loads
both skill roots, all already linked.

claude-md/opencode-header.md

@@ -0,0 +1 @@
+Screenshots: stored in ~/downloads/screenshots, with date time in the filename

nix/home.nix

@@ -1,5 +1,6 @@
-# Home-manager module: link centralized agent skills into Claude Code + Codex.
-# Usage: add this flake as an input, then import this module in your home config.
+# Home-manager module: link centralized agent skills into Claude Code, Codex,
+# Pi and opencode. Usage: add this flake as an input, then import this module
+# in your home config.
 #
 #   inputs.agent-skills.url = "git+https://git.naps.pt/yolo/agent-skills.git";
 #   # in home.nix imports: inputs.agent-skills.homeModules.default
@@ -9,9 +10,20 @@
 # recursive=true links each FILE individually, so machine-local skills can still
 # live alongside the managed ones in the same dir (a whole-dir symlink would not).
 { agent-skills }:
-{ config, lib, ... }:
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
 let
   cfg = config.programs.agentSkills;
+
+  # Pi and opencode have no `@file` imports in context files, so the shared
+  # fragments are concatenated into one AGENTS.md per tool.
+  concatMd =
+    name: files:
+    pkgs.writeText name (lib.concatMapStringsSep "\n" builtins.readFile files);
 in
 {
   options.programs.agentSkills.machine = lib.mkOption {
@@ -65,6 +77,31 @@ in
     # Entry files: machine-local sections + @imports of the fragments above.
     ".claude/CLAUDE.md".source = "${agent-skills}/entry/CLAUDE.md";
     ".codex/AGENTS.md".source = "${agent-skills}/entry/codex-AGENTS.md";
+
+    # Pi: skills need no wiring — pi reads ~/.agents/skills, linked above.
+    # Settings stay unmanaged: pi writes ~/.pi/agent/settings.json itself.
+    ".pi/agent/AGENTS.md".source = concatMd "pi-AGENTS.md" [
+      "${agent-skills}/claude-md/machines/${cfg.machine}.md"
+      "${agent-skills}/claude-md/operating.md"
+      "${agent-skills}/claude-md/writing.md"
+      "${agent-skills}/claude-md/code-comments.md"
+      "${agent-skills}/claude-md/RTK.md"
+    ];
+
+    # opencode auto-loads skills from ~/.claude/skills and ~/.agents/skills,
+    # so only the rules file and commands need linking here.
+    ".config/opencode/AGENTS.md".source = concatMd "opencode-AGENTS.md" [
+      "${agent-skills}/claude-md/opencode-header.md"
+      "${agent-skills}/claude-md/machines/${cfg.machine}.md"
+      "${agent-skills}/claude-md/operating.md"
+      "${agent-skills}/claude-md/writing.md"
+      "${agent-skills}/claude-md/code-comments.md"
+      "${agent-skills}/claude-md/RTK.md"
+    ];
+    ".config/opencode/commands" = {
+      source = "${agent-skills}/commands";
+      recursive = true;
+    };
   };
 }
 # Hook wiring lives in ~/.claude/settings.json, which this module does not own.