fix: update claude-opus references to 4.7

[poe-code-agent]

Summary

• update claude-opus-4.6 references that should track the newest Opus model to claude-opus-4.7
• refresh CLI constants, model help example text, and experiment template example
• update affected tests/fixtures to reflect the new model id

Validation

• npm run test:unit -- src/cli/constants.test.ts src/cli/commands/models-command.test.ts src/cli/commands/spawn-command.test.ts src/cli/cli-scripts.test.ts src/cli/cli-utilities.test.ts src/cli/poe-agent-main.test.ts src/providers/providers.test.ts src/sdk/sdk-core.test.ts
• npm run test:unit -- src/cli/commands/commands.test.ts -t "configure command"
• npm run screenshot-poe-code -- models --help
• git push hook also ran full npm run test (all unit suites passed)

Closes #209

[poe-code-agent]

Review result: changes required.

I reviewed all 11 changed files and found one missed src/ reference:

• src/cli/logger.test.ts still uses Claude-Opus-4.6 (assertion and expected output).

Given issue #209 specifically targets src/ references that should track the latest Opus model, this should be updated to Claude-Opus-4.7 before merge.