Speed up shell startup 9x (1.9s → 0.2s)

Lazy-load Intel oneAPI setvars.sh (~1.5s) via wrapper functions that
source the environment on first use of icc/icx/ifort/etc.

Cache all shell completion outputs to ~/.cache/bash.d/ so they are
sourced from disk instead of regenerated via subprocess on every
shell start.  Cache invalidates automatically when the tool binary
is updated.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

20-oneapi

@@ -1,13 +1,45 @@
 # shellcheck shell=bash
-# Intel oneAPI toolkit — source the environment setup if installed
-# shellcheck disable=SC1090
+# Intel oneAPI toolkit — lazy-loaded to avoid ~1.5s startup penalty.
+# The full environment is sourced on first use of any Intel compiler/tool.
+# To load manually: _load_oneapi
+
 ONEAPI_SETVARS="/opt/intel/oneapi/setvars.sh"
+
 if [[ -f "$ONEAPI_SETVARS" ]]; then
-    . "$ONEAPI_SETVARS" --force > /dev/null
-    if [[ -n "$ONEAPI_ROOT" ]]; then
-        case ":${LD_LIBRARY_PATH}:" in
-            *":${ONEAPI_ROOT}/lib:"*) ;;
-            *) export LD_LIBRARY_PATH="${ONEAPI_ROOT}/lib${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}" ;;
-        esac
-    fi
+    _load_oneapi() {
+        # Guard against double-loading
+        if [[ "${_ONEAPI_LOADED:-0}" -eq 1 ]]; then
+            return
+        fi
+        _ONEAPI_LOADED=1
+
+        # Remove the lazy-load wrappers before sourcing
+        local _cmd
+        for _cmd in icc icpc icx icpx ifort ifx dpcpp; do
+            unset -f "$_cmd" 2>/dev/null
+        done
+
+        # shellcheck disable=SC1090
+        . "$ONEAPI_SETVARS" --force > /dev/null
+
+        if [[ -n "$ONEAPI_ROOT" ]]; then
+            case ":${LD_LIBRARY_PATH}:" in
+                *":${ONEAPI_ROOT}/lib:"*) ;;
+                *) export LD_LIBRARY_PATH="${ONEAPI_ROOT}/lib${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}" ;;
+            esac
+        fi
+    }
+
+    # Create wrapper functions for common Intel tools that trigger lazy-load
+    _oneapi_lazy_wrap() {
+        local cmd="$1"
+        # shellcheck disable=SC2139
+        eval "${cmd}() { _load_oneapi; command ${cmd} \"\$@\"; }"
+    }
+
+    for _oneapi_cmd in icc icpc icx icpx ifort ifx dpcpp; do
+        _oneapi_lazy_wrap "$_oneapi_cmd"
+    done
+    unset -f _oneapi_lazy_wrap
+    unset _oneapi_cmd
 fi