Fold the default-agents package into the agent module

[TheGreatAxios]

Summary

• The agent profile contract (profile-types.ts) and the built-in greybeard/critique profiles (default-agents.ts) live in src/agent/; the @intercode/default-agents workspace package no longer exists
• Agent plugins and local profiles are data validated at load time, so nothing outside the repo imports these types; the workspace has a single first-party package

Verification

• bun run typecheck and bun run build exit 0; bun test passes 2757 tests with only the 2 known pre-existing failures in vendor/intx-inference/src/assembly.test.ts
• No references to @intercode/default-agents or packages/agents remain outside the diff

Closes CL-4045

[TheGreatAxios]

Self-review (code-review skill) returned clean.

[linear-code]

CL-4045 Fold @intercode/default-agents into src and drop the workspace package

packages/agents (@intercode/default-agents) is 124 lines of agent-profile types and the REASONING_EFFORTS constant, consumed by exactly four files in src/. Its stated purpose — letting plugin authors depend on the type contract — is moot: agent plugins and local profiles are data (JSON/YAML under .agents/agents/, plugin-provided profiles) validated at the boundary, so nothing outside the repo imports these types.

Fold packages/agents/src/types.ts and index.ts into src/agent/ (e.g. merge into profiles.ts or a sibling module), update the four importers (src/config/settings.ts, src/plugins/data-only-agent.ts, src/provider/reasoning-effort.ts, src/agent/profiles.ts), remove the workspace entry from root package.json, and delete packages/. Per repo convention, delete the old path outright — no re-export shims.

Do after PR #152 (license) merges to keep that review surface clean.

Review in Linear

[TheGreatAxios]

Independent review pass (pull-request-review + code-review skills): single-commit scope matches CL-4045, subject/body audits clean (git log --format='%s'|'%b' | awk 'length > 72' both empty), no binary markers in --stat, diff is the package fold with no unrelated changes, and bun test passes with only the two known pre-existing vendor failures.