feat(manifest): [build].profile sets the project default build profile; v0.0.76

Adds a per-project default-profile knob so a plain `mcpp build` can use a
project's preferred profile without typing --profile every time. The global
convention default stays "release"; `[build] profile = "dev"` overrides it for
that project; a `--profile <name>` flag still overrides everything.

Precedence (prepare.cppm): --profile flag > [build].profile > "release".
manifest.cppm: parse build.profile into buildConfig.defaultProfile.

Test: tests/e2e/87_build_default_profile.sh ([build].profile=dev → plain build
is -O0 -g; --profile release overrides to -O2).

Author: Sunrisepeak

mcpp.toml

@@ -1,6 +1,6 @@
 [package]
 name        = "mcpp"
-version     = "0.0.75"
+version     = "0.0.76"
 description = "Modern C++ build & package management tool"
 license     = "Apache-2.0"
 authors     = ["mcpp-community"]

src/build/prepare.cppm

@@ -557,7 +557,11 @@ prepare_build(bool print_fingerprint,
     // Resolve the build profile: --profile (default "release") → built-in
     // defaults, overlaid by any [profile.<name>] from the manifest → buildConfig.
     {
-        std::string pname = overrides.profile.empty() ? "release" : overrides.profile;
+        // Precedence: --profile flag > [build].profile (project default) >
+        // "release" (global convention).
+        std::string pname = !overrides.profile.empty()             ? overrides.profile
+                          : !m->buildConfig.defaultProfile.empty() ? m->buildConfig.defaultProfile
+                          :                                          "release";
         mcpp::manifest::Profile pr;
         if (pname == "dev" || pname == "debug") { pr.optLevel = "0"; pr.debug = true; }
         else if (pname == "dist")               { pr.optLevel = "3"; pr.strip = true; }

src/manifest.cppm

@@ -148,6 +148,11 @@ struct BuildConfig {
     bool                                debug    = false; // -g
     bool                                lto      = false; // -flto
     bool                                strip    = false; // link -s
+    // `[build].profile` — the project's DEFAULT profile when no --profile is
+    // passed. The global convention default stays "release"; this lets a project
+    // opt its plain `mcpp build` into e.g. "dev" without typing --profile. A
+    // `--profile <name>` flag always overrides it.
+    std::string                         defaultProfile;
 };
 
 // `[runtime]` — requirements needed when launching built binaries.
@@ -1118,6 +1123,7 @@ std::expected<Manifest, ManifestError> parse_string(std::string_view content,
     if (auto v = doc->get_string_array("build.cxxflags")) m.buildConfig.cxxflags = *v;
     if (auto v = doc->get_string_array("build.ldflags"))  m.buildConfig.ldflags  = *v;
     if (auto v = doc->get_string("build.c_standard"))     m.buildConfig.cStandard = *v;
+    if (auto v = doc->get_string("build.profile"))        m.buildConfig.defaultProfile = *v;
     if (auto v = doc->get_string("build.macos_deployment_target"))
         m.buildConfig.macosDeploymentTarget = *v;
     for (auto const& flag : m.buildConfig.cxxflags) {

src/toolchain/fingerprint.cppm

@@ -18,7 +18,7 @@ import mcpp.toolchain.detect;
 
 export namespace mcpp::toolchain {
 
-inline constexpr std::string_view MCPP_VERSION = "0.0.75";
+inline constexpr std::string_view MCPP_VERSION = "0.0.76";
 
 struct FingerprintInputs {
     Toolchain                       toolchain;

tests/e2e/87_build_default_profile.sh

@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+# 87_build_default_profile.sh — `[build].profile` sets a project's DEFAULT build
+# profile, so plain `mcpp build` uses it without typing --profile. The global
+# convention default stays "release"; a `--profile <name>` flag overrides the
+# project default. See .agents/docs/2026-06-29-manifest-environment-and-platform-design.md.
+set -e
+
+TMP=$(mktemp -d)
+trap "rm -rf $TMP" EXIT
+cd "$TMP"
+
+mkdir -p app/src
+cat > app/mcpp.toml <<'EOF'
+[package]
+name    = "app"
+version = "0.1.0"
+
+# Project opts its plain `mcpp build` into the dev profile.
+[build]
+profile = "dev"
+EOF
+cat > app/src/main.cpp <<'EOF'
+int main() { return 0; }
+EOF
+
+cd app
+
+# Plain build → the [build].profile default ("dev": -O0 -g), no --profile typed.
+"$MCPP" build > b.log 2>&1 || { cat b.log; echo "FAIL: build errored"; exit 1; }
+grep -q '\-O0' compile_commands.json || { echo "FAIL: [build].profile=dev did not yield -O0"; cat compile_commands.json; exit 1; }
+grep -q '\-g\b' compile_commands.json || { echo "FAIL: [build].profile=dev did not yield -g (debug)"; exit 1; }
+
+# An explicit --profile overrides the project default (release → -O2, no -g debug).
+"$MCPP" build --profile release > b2.log 2>&1 || { cat b2.log; echo "FAIL: --profile release build errored"; exit 1; }
+grep -q '\-O2' compile_commands.json || { echo "FAIL: --profile release did not override to -O2"; cat compile_commands.json; exit 1; }
+
+echo "OK"