Rename 9harness to 9agents; README, file-backed qids, worded errors

- 9harness/ becomes 9agents/ (build option -D9agents, package paths).
- 9agents serves /README, reports qid paths from the file's (dev, ino)
  and qid versions that move with the file, and names its refusals.

1 files changed, 54 insertions, 0 deletions

diff --git a/9agents/build.zig b/9agents/build.zig
new file mode 100644
index 0000000..0a63d9b
--- /dev/null
+++ b/9agents/build.zig
@@ -0,0 +1,54 @@
+//! Build fragment for 9agents: the coding-agents fs daemon (binary `9agents`),
+//! a read-only fresh-from-disk 9P2000 view of every harness's state,
+//! posted by default under the name `agents`. It is `@import`ed by the
+//! root build.zig and called with the root builder, so every `b.path(...)`
+//! here is relative to the cloud9 root (hence the `9agents/` prefix),
+//! every option is defined by the root and every step it registers lands
+//! in the root's step list under the `9agents` prefix.
+//!
+//! Steps: 9agents, 9agents-test, 9agents-itest.
+const std = @import("std");
+
+pub const Context = struct {
+    target: std.Build.ResolvedTarget,
+    optimize: std.builtin.OptimizeMode,
+    cloud9: *std.Build.Module,
+    /// The 9ns binary, for the --mntgen money shot in the integration
+    /// suite; null when 9ns is disabled, in which case the mntgen
+    /// section of the suite is skipped.
+    ns: ?*std.Build.Step.Compile,
+};
+
+pub const Artifacts = struct {
+    exe: *std.Build.Step.Compile,
+    /// `9agents-test`: the tree's unit tests (exclusions, path safety,
+    /// node ids, vanishing files — all against a fake HOME).
+    test_step: *std.Build.Step,
+    /// `9agents-itest`: test/e2e.sh (fixture roots + scratch registry,
+    /// plus the real-registry end-to-end when the `agents` name is free).
+    itest_step: *std.Build.Step,
+};
+
+pub fn add(b: *std.Build, ctx: Context) Artifacts {
+    const mod = b.createModule(.{
+        .root_source_file = b.path("9agents/src/main.zig"),
+        .target = ctx.target,
+        .optimize = ctx.optimize,
+        .imports = &.{.{ .name = "cloud9", .module = ctx.cloud9 }},
+    });
+    const exe = b.addExecutable(.{ .name = "9agents", .root_module = mod });
+    const install = b.addInstallArtifact(exe, .{});
+    b.getInstallStep().dependOn(&install.step);
+    b.step("9agents", "Build and install only the coding-agents fs daemon").dependOn(&install.step);
+
+    const test_step = b.step("9agents-test", "Run the 9agents tree's unit tests (fake HOME; never the live roots)");
+    test_step.dependOn(&b.addRunArtifact(b.addTest(.{ .root_module = mod })).step);
+
+    const itest_step = b.step("9agents-itest", "Run 9agents/test/e2e.sh (posted name, reads, cmp of a transcript, mntgen mount, exclusions, live appends)");
+    const run = b.addSystemCommand(&.{"bash"});
+    run.addFileArg(b.path("9agents/test/e2e.sh"));
+    run.addArtifactArg(exe);
+    if (ctx.ns) |ns| run.addArtifactArg(ns);
+    itest_step.dependOn(&run.step);
+    return .{ .exe = exe, .test_step = test_step, .itest_step = itest_step };
+}