Define configuration, environment, signal, and shutdown conventions

[codeforester]

Parent: #214

Train position: 15 of 26
Phase: P2 — Project kit and deterministic distribution

Problem

A framework needs one application model beyond parsing: deterministic configuration precedence, safe noninteractive behavior, lifecycle signals, cleanup, and shutdown. Without conventions, every consumer must invent incompatible policies around otherwise shared runtime primitives.

Acceptance criteria

• Define and implement deterministic precedence across CLI values, environment, explicit project or user configuration, and defaults, including value provenance.
• Treat configuration as data by default; never silently execute untrusted shell content, and fail clearly for explicitly requested missing or malformed files.
• Standardize common help, version, verbosity, color, dry-run, noninteractive, prompt, and configuration options without forcing every application to enable them.
• Define INT, TERM, HUP, normal-return, fatal-error, and secondary-cleanup behavior with stable statuses and exactly-once LIFO cleanup.
• Prevent secrets from appearing in help, effective-configuration reports, provenance, completions, or lifecycle diagnostics.
• Provide composable application hooks and contract tests without enlarging the stable Core with optional policy.

Dependencies

• Harden cleanup deletion, trap, and resource-unwinding contracts #221
• Standardize public error, status, output, and mutation semantics #224
• Make base-bash a conventional, stable application launcher #227
• Provide a declarative CLI contract with help, validation, and subcommands #228