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/process/process_exit_codes.toml

@@ -0,0 +1,40 @@
+name = "process_exit_codes"
+category = "process"
+mode = "solve"
+description = """
+Read commands from stdin, one per line. Execute each command as a subprocess.
+For each command, print: "command: exit_code" where command is the original command text
+and exit_code is the numeric exit code of the process.
+
+After all commands, print a blank line followed by a summary line:
+"passed: N, failed: M"
+where N is the count of commands with exit code 0, and M is the count with non-zero exit codes.
+"""
+
+[[test_cases]]
+stdin = """true
+false
+echo hello
+test -f /nonexistent"""
+expected_stdout = """true: 0
+false: 1
+echo hello: 0
+test -f /nonexistent: 1
+
+passed: 2, failed: 2"""
+
+[[test_cases]]
+stdin = """true
+true
+true"""
+expected_stdout = """true: 0
+true: 0
+true: 0
+
+passed: 3, failed: 0"""
+
+[[test_cases]]
+stdin = "false"
+expected_stdout = """false: 1
+
+passed: 0, failed: 1"""