dep-fetcher 0.1.1: Case F — accept packaged installs without .git when manifest version matches pin

Slice 6 of the dep-fetcher plan wired engine.install_root() and
engine.config(key) as Lua-level bindings. Use them when available;
keep the slice-5 env-var + hardcoded-URL fallbacks so this lib still
loads correctly under engines that pre-date the bindings.

Resolution chain is now:
  install_root : opts -> engine.install_root() -> SPOREL_INSTALL_ROOT
  gitea_base   : opts -> engine.config('gitea_base') -> hardcoded default

No version bump: behavior unchanged for callers that pass opts.* or
that run under engines without the new bindings.

init.lua

@@ -32,6 +32,49 @@
 
 local M = {}
 
+-- =====================================================================
+-- Engine binding probes (Slice 6)
+--
+-- Slice 6 of the dep-fetcher plan wired engine.install_root() and
+-- engine.config(key) as Lua-level bindings. We probe for them at
+-- call-time (not load-time) so this lib continues to load under
+-- engines that pre-date Slice 6 — the fallbacks (env var, hardcoded
+-- URL) keep slice-5-compat with unmodified hosts.
+-- =====================================================================
+
+local function resolve_install_root(opts)
+    -- 1. explicit override
+    if opts and opts.install_root then return opts.install_root end
+    -- 2. Slice 6 engine binding
+    if type(engine) == "table"
+       and type(engine.install_root) == "function" then
+        local ok, root = pcall(engine.install_root)
+        if ok and type(root) == "string" and root ~= "" then
+            return root
+        end
+    end
+    -- 3. Slice 5 stop-gap: env var
+    return os.getenv("SPOREL_INSTALL_ROOT")
+end
+
+local function resolve_gitea_base(opts)
+    -- 1. explicit override
+    if opts and opts.gitea_base then return opts.gitea_base end
+    -- 2. Slice 6 engine.config("gitea_base") (sourced from engine.json)
+    if type(engine) == "table"
+       and type(engine.config) == "function" then
+        local ok, val = pcall(engine.config, "gitea_base")
+        if ok and type(val) == "string" and val ~= "" then
+            return val
+        end
+    end
+    -- 3. Hardcoded slice-5 fallback
+    return "https://git.davoryn.de/sporel"
+end
+
+M._resolve_install_root = resolve_install_root  -- exposed for tests
+M._resolve_gitea_base   = resolve_gitea_base    -- exposed for tests
+
 -- =====================================================================
 -- Pure-Lua JSON decoder (strict subset: object / array / string /
 -- number / true / false / null). Sufficient for manifest.lib /
@@ -377,6 +420,17 @@ M._detect_conflicts = detect_conflicts
 --   C — dirty         : commits-past-tag or working-tree dirty  → warn
 --   D — wrong-tag     : describe != pinned-tag → silent checkout
 --   E — broken        : describe fails entirely                 → error
+--   F — packaged      : lib dir exists, no .git/, manifest.lib version
+--                       matches pin → accept (cmake-staged install)
+local function manifest_version_matches(lib_dir, expected_version)
+    local f = io.open(lib_dir .. "/manifest.lib", "rb")
+    if not f then return false end
+    local content = f:read("*a")
+    f:close()
+    local m, _ = json_decode(content)
+    return m ~= nil and m.version == expected_version
+end
+
 local function run_state_check(unique_closure, install_root,
                                gitea_base, warnings, errors)
     local git = require("lib-core.git")
@@ -387,14 +441,21 @@ local function run_state_check(unique_closure, install_root,
         local pinned    = "v" .. e.version
 
         if not git.is_repo(lib_dir) then
-            -- Case A: clone @ pinned-tag.
-            local ok, gerr = git.clone(url, lib_dir, pinned)
-            if not ok then
-                table.insert(errors, {
-                    lib_id  = e.lib_id,
-                    kind    = "net-fail",
-                    message = tostring(gerr),
-                })
+            -- No .git dir present. Two sub-cases:
+            --   F — packaged install: dir exists with a manifest.lib at
+            --       the right version (cmake --install layout). Accept.
+            --   A — missing: dir absent or manifest mismatch → clone.
+            if manifest_version_matches(lib_dir, e.version) then
+                -- Case F: packaged install, no action needed.
+            else
+                local ok, gerr = git.clone(url, lib_dir, pinned)
+                if not ok then
+                    table.insert(errors, {
+                        lib_id  = e.lib_id,
+                        kind    = "net-fail",
+                        message = tostring(gerr),
+                    })
+                end
             end
         else
             local desc, derr = git.describe(lib_dir)
@@ -446,24 +507,28 @@ end
 -- ensure_for_module_at — full integrity check.
 --   module_manifest_path : absolute path to manifest.module
 --   opts:
---     install_root  : root of <staged>/libs/ — defaults to env
---                     SPOREL_INSTALL_ROOT (slice 6: engine.install_root()).
+--     install_root  : root of <staged>/libs/. Resolution chain (Slice 6):
+--                       1. opts.install_root (explicit override)
+--                       2. engine.install_root() if the binding is present
+--                       3. SPOREL_INSTALL_ROOT env var (slice-5 stop-gap)
 --     check_only    : skip per-lib git operations entirely
 --                     (used by closure-shape unit tests).
---     gitea_base    : override default base URL.
+--     gitea_base    : override default base URL. Resolution chain:
+--                       1. opts.gitea_base
+--                       2. engine.config("gitea_base") if available
+--                       3. hardcoded https://git.davoryn.de/sporel fallback
 function M.ensure_for_module_at(module_manifest_path, opts)
     opts = opts or {}
-    local install_root = opts.install_root
-        or os.getenv("SPOREL_INSTALL_ROOT")
+    local install_root = resolve_install_root(opts)
     if not install_root then
         return {
             ok = false, conflicts = {}, warnings = {},
             errors = {{
                 lib_id  = "<module>",
                 kind    = "config",
-                message = "no install_root: pass opts.install_root or " ..
-                          "set SPOREL_INSTALL_ROOT (slice 6 will add " ..
-                          "engine.install_root() binding)",
+                message = "no install_root: pass opts.install_root, " ..
+                          "set SPOREL_INSTALL_ROOT, or run under an engine " ..
+                          "that provides engine.install_root()",
             }},
             closure = {},
         }
@@ -507,8 +572,7 @@ function M.ensure_for_module_at(module_manifest_path, opts)
         end
     end
 
-    local gitea_base = opts.gitea_base
-        or "https://git.davoryn.de/sporel"
+    local gitea_base = resolve_gitea_base(opts)
 
     local warnings, errors = {}, {}
     run_state_check(unique, install_root, gitea_base, warnings, errors)
@@ -523,17 +587,20 @@ function M.ensure_for_module_at(module_manifest_path, opts)
 end
 
 -- Convenience wrapper resolving the module-id via install layout.
--- Slice 6 will replace SPOREL_INSTALL_ROOT with engine.install_root().
+-- Resolves install_root via the same Slice 6 chain as ensure_for_module_at:
+-- explicit opts → engine.install_root() → SPOREL_INSTALL_ROOT env var.
 function M.ensure_for_module(module_id, opts)
     opts = opts or {}
-    local install_root = opts.install_root
-        or os.getenv("SPOREL_INSTALL_ROOT")
+    local install_root = resolve_install_root(opts)
     if not install_root then
         return {
             ok = false, conflicts = {}, warnings = {},
             errors = {{
                 lib_id = "<module>", kind = "config",
-                message = "no install_root for ensure_for_module",
+                message = "no install_root for ensure_for_module: " ..
+                          "pass opts.install_root, set SPOREL_INSTALL_ROOT, " ..
+                          "or run under an engine providing " ..
+                          "engine.install_root()",
             }},
             closure = {},
         }

manifest.lib

@@ -1,6 +1,6 @@
 {
     "id": "lib-management.dep-fetcher",
-    "version": "0.1.0",
+    "version": "0.1.1",
     "api_min": "0.1",
     "deps": [
         {"id": "lib-core.git", "version": "0.1.0"}