chore: improve GenAI tests in PR descriptions

[ovitrif]

This PR ports the shared agent PR-description guidance from synonymdev/bitkit-android#928 to the iOS repo.

Description

This PR:

1. Moves durable /pr and /release command specs into .agents/commands.
2. Keeps .claude/commands as a compatibility symlink to the same files.
3. Updates /pr guidance so generated QA notes split manual validation from automated check coverage.
4. Adds iOS-specific examples for manual QA and automated coverage summaries.

Linked Issues/Tasks

Ports synonymdev/bitkit-android#928

Screenshot / Video

N/A

QA Notes

Manual Tests

• 1. Repo checkout → inspect .claude/commands: pr.md and release.md resolve through the symlink.
• 2. Agent docs → open AGENTS.md: durable PR command behavior points to .agents/commands/pr.md.
• 3. /pr --dry in Claude Code → generate a PR body: QA Notes contains separate Manual Tests and Automated Checks sections.

Automated Checks

• git diff --check
• Symlink validation: .claude/commands resolves to ../.agents/commands, and both command specs are reachable through it.
• Release command move validated: .agents/commands/release.md matches the original tracked command file exactly.

[piotr-iohk]

lgtm

[ovitrif]

Shouldn't have to wait or integration tests and unit tests on PRs that don't change code contributing to output binaries during compilation.