Add doctor selection module and CLI for deterministic read-only selection

[binrogithub]

Motivation

• Provide a non-mutating "doctor" selection utility that inspects available resources and chooses one deterministically without creating or modifying resources.
• Allow tooling to consume a stable ctx_patch and human-readable summary to drive downstream automation or dry-run workflows.

Description

• Add package scaffolding hc_agent and CLI package hc_agent/cli to host the new functionality.
• Implement hc_agent/doctor.py which performs read-only listings via a list_resources callable and selects a candidate using precedence: explicit input match > resources tagged with a default tag > stable tie-break by (name, id), and returns a DoctorResult with ctx_patch and summary.
• Implement tag normalization and parsing logic in hc_agent/doctor.py to support tag values expressed as mappings, lists, or strings and to recognize common truthy values for the default tag.
• Add CLI entry hc_agent/cli/cmd_doctor.py which accepts --resources-file or JSON on stdin, --explicit, and --default-tag, invokes doctor.run_doctor, and emits a JSON object with ctx_patch and summary to stdout.

Testing

• No automated tests were run for these changes.

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Codex Task