Reorganize task categories from opaque a/b to descriptive names

Replace category_a/category_b directories with algorithm, pipeline,
environment, filesystem, and process. Add separate mode field (solve/convert)
to decouple orchestration from capability grouping. Add per-category
summary and questionnaire breakdowns to both terminal report and HTML export.

tasks/environment/env_path_builder.toml

@@ -0,0 +1,40 @@
+name = "env_path_builder"
+category = "environment"
+mode = "convert"
+description = """
+Read directory paths from stdin, one per line.
+Append each to the MYPATH environment variable (colon-separated), skipping duplicates.
+The initial value of MYPATH is provided via the environment (may be empty).
+Print the final value of MYPATH to stdout.
+"""
+
+bash_source = """
+#!/bin/bash
+while IFS= read -r dir || [[ -n "$dir" ]]; do
+    if [[ -z "$MYPATH" ]]; then
+        export MYPATH="$dir"
+    elif [[ ":$MYPATH:" != *":$dir:"* ]]; then
+        export MYPATH="$MYPATH:$dir"
+    fi
+done
+echo "$MYPATH"
+"""
+
+[[test_cases]]
+stdin = """/usr/local/bin
+/usr/bin
+/usr/local/bin
+/opt/bin"""
+expected_stdout = "/usr/local/bin:/usr/bin:/opt/bin"
+env = { "MYPATH" = "" }
+
+[[test_cases]]
+stdin = """/new/path
+/existing"""
+expected_stdout = "/already/here:/new/path:/existing"
+env = { "MYPATH" = "/already/here" }
+
+[[test_cases]]
+stdin = "/only"
+expected_stdout = "/only"
+env = { "MYPATH" = "" }