feat(apollo3): add build orchestrator, toolchain, and board definitions

crates/fbuild-build/src/apollo3/README.md

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+# Apollo3 Build Orchestrator
+
+Build orchestrator for the Ambiq Apollo3 platform (ARM Cortex-M4F). Uses the generic ARM compiler/linker with mbed-os response files from the SparkFun Arduino Apollo3 core.

crates/fbuild-build/src/apollo3/configs/README.md

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+# Apollo3 MCU Configurations
+
+Embedded JSON configs for Apollo3 (Ambiq Micro) ARM Cortex-M4F MCUs.

crates/fbuild-build/src/apollo3/configs/apollo3.json

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+{
+  "name": "Apollo3",
+  "description": "Ambiq Micro Apollo3 (ARM Cortex-M4F)",
+  "architecture": "arm-cortex-m4f",
+
+  "compiler_flags": {
+    "common": [
+      "-mcpu=cortex-m4",
+      "-mthumb",
+      "-mfloat-abi=hard",
+      "-mfpu=fpv4-sp-d16",
+      "-fdata-sections",
+      "-ffunction-sections",
+      "-fmessage-length=0",
+      "-fno-exceptions",
+      "-fomit-frame-pointer",
+      "-funsigned-char",
+      "-MMD"
+    ],
+    "c": [
+      "-std=gnu11"
+    ],
+    "cxx": [
+      "-std=gnu++14",
+      "-fno-rtti"
+    ]
+  },
+
+  "linker_flags": [
+    "-mcpu=cortex-m4",
+    "-mthumb",
+    "-mfloat-abi=hard",
+    "-mfpu=fpv4-sp-d16",
+    "-Wl,--gc-sections",
+    "-Wl,-n"
+  ],
+
+  "linker_libs": [
+    "-lsupc++",
+    "-lstdc++",
+    "-lm"
+  ],
+
+  "objcopy": {
+    "output_format": "binary",
+    "remove_sections": []
+  },
+
+  "profiles": {
+    "release": {
+      "compile_flags": ["-Os"],
+      "link_flags": []
+    },
+    "quick": {
+      "compile_flags": ["-Os"],
+      "link_flags": []
+    }
+  },
+
+  "defines": [
+    ["ARDUINO", "10808"],
+    "MBED_NO_GLOBAL_USING_DIRECTIVE",
+    "CORDIO_ZERO_COPY_HCI"
+  ]
+}

crates/fbuild-build/src/apollo3/mcu_config.rs

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+//! Data-driven Apollo3 MCU configuration from embedded JSON.
+//!
+//! Maps Apollo3 MCU names to the appropriate ARM Cortex-M4F configuration.
+
+use fbuild_core::Result;
+
+use crate::generic_arm::ArmMcuConfig;
+
+const APOLLO3_JSON: &str = include_str!("configs/apollo3.json");
+
+/// Load MCU configuration for the Apollo3.
+pub fn get_apollo3_config_for_mcu(mcu: &str) -> Result<ArmMcuConfig> {
+    let json = match mcu {
+        "apollo3" => APOLLO3_JSON,
+        _ => {
+            // Default to Apollo3 for any Ambiq MCU variant
+            if mcu.starts_with("ama3b") || mcu.contains("apollo") {
+                APOLLO3_JSON
+            } else {
+                return Err(fbuild_core::FbuildError::ConfigError(format!(
+                    "unsupported Apollo3 MCU: '{}' (supported: apollo3, ama3b*)",
+                    mcu
+                )));
+            }
+        }
+    };
+    serde_json::from_str(json).map_err(|e| {
+        fbuild_core::FbuildError::ConfigError(format!(
+            "failed to parse Apollo3 MCU config for '{}': {}",
+            mcu, e
+        ))
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_load_apollo3_config() {
+        let config = get_apollo3_config_for_mcu("apollo3").unwrap();
+        assert_eq!(config.name, "Apollo3");
+        assert_eq!(config.architecture, "arm-cortex-m4f");
+    }
+
+    #[test]
+    fn test_load_apollo3_ama3b_variant() {
+        let config = get_apollo3_config_for_mcu("ama3b1kk").unwrap();
+        assert_eq!(config.name, "Apollo3");
+    }
+
+    #[test]
+    fn test_unsupported_mcu() {
+        assert!(get_apollo3_config_for_mcu("stm32f103").is_err());
+    }
+
+    #[test]
+    fn test_apollo3_compiler_flags() {
+        let config = get_apollo3_config_for_mcu("apollo3").unwrap();
+        assert!(config
+            .compiler_flags
+            .common
+            .contains(&"-mcpu=cortex-m4".to_string()));
+        assert!(config
+            .compiler_flags
+            .common
+            .contains(&"-mthumb".to_string()));
+        assert!(config
+            .compiler_flags
+            .common
+            .contains(&"-mfloat-abi=hard".to_string()));
+        assert!(config
+            .compiler_flags
+            .common
+            .contains(&"-mfpu=fpv4-sp-d16".to_string()));
+    }
+}

crates/fbuild-build/src/apollo3/mod.rs

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+//! Apollo3 platform build support (Ambiq Micro Apollo3 / SparkFun Artemis).
+
+pub mod mcu_config;
+pub mod orchestrator;
+
+pub use orchestrator::Apollo3Orchestrator;
+
+/// Apollo3 platform support.
+pub struct Apollo3PlatformSupport;
+
+impl crate::PlatformSupport for Apollo3PlatformSupport {
+    fn create_orchestrator(&self) -> Box<dyn crate::BuildOrchestrator> {
+        orchestrator::create()
+    }
+
+    fn install_deps(&self, project_dir: &std::path::Path) -> fbuild_core::Result<()> {
+        use fbuild_packages::Package;
+        let tc = fbuild_packages::toolchain::ArmGcc8Toolchain::new(project_dir);
+        Package::ensure_installed(&tc)?;
+        tracing::info!("ARM GCC 8 toolchain installed");
+        Ok(())
+    }
+
+    fn default_board_id(&self) -> &str {
+        "SparkFun_RedBoard_Artemis_ATP"
+    }
+}