Integrate old-svovel config: paths, aliases, completions

Add ~/bin PATH, rbenv (disabled), debuginfod, sccache, LESS/ag/task
aliases, and cargo/rustup completions. Removes old-svovel/ directory.

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

30-aliases

@@ -0,0 +1,13 @@
+# shellcheck shell=bash
+# Miscellaneous aliases and settings
+
+export LESS=-R
+
+if command -v ag &>/dev/null; then
+    alias ag='ag --pager=less -A3 -B3 -C2'
+fi
+
+# Show task list on interactive shell startup
+if [[ $- == *i* ]] && command -v task &>/dev/null; then
+    task
+fi