feat(go-sdk): add AgentRouter pattern for modular agent organisation Fixes #98

[dhanadeep6]

Summary

Adds Router, RouterOptions, and Agent.IncludeRouter to the Go SDK,
bringing it to parity with the Python AgentRouter and TypeScript AgentRouter
already in the repo.

Files changed

File	Change
sdk/go/agent/router.go	New — complete implementation
sdk/go/agent/router_test.go	New — 11 integration tests

Usage

userRouter := agent.NewRouter()
userRouter.RegisterReasoner("get-profile", getProfileFn,
    agent.WithDescription("Fetch a user by ID"))
userRouter.RegisterSkill("validate-email", validateEmailFn)

a.IncludeRouter(userRouter, agent.RouterOptions{
    Prefix: "users",
    Tags:   []string{"user-management"},
})
// Registers: users.get-profile, users.validate-email

// Nested:
adminRouter := agent.NewRouter()
adminRouter.IncludeRouter(userRouter, agent.RouterOptions{Prefix: "users"})
a.IncludeRouter(adminRouter, agent.RouterOptions{Prefix: "admin"})
// Registers: admin.users.get-profile, admin.users.validate-email

Design notes

• No new exported types — uses existing HandlerFunc and ReasonerOption
• withAppendTags (unexported) merges RouterOptions.Tags without clobbering per-handler WithReasonerTags
• Agent.IncludeRouter calls existing RegisterReasoner only — DID auth, VC generation, and tracing fire unchanged
• A Router is a pure immutable tree — safe to mount under multiple prefixes or into multiple agents

Test results

--- PASS: TestRouter_FlatMount
--- PASS: TestRouter_NoPrefix
--- PASS: TestRouter_NestedRouters
--- PASS: TestRouter_DeeplyNested
--- PASS: TestRouter_SharedRouter
--- PASS: TestRouter_EmptyRouter
--- PASS: TestRouter_HandlerFires
--- PASS: TestRouter_WithDescription
--- PASS: TestRouter_WithReasonerTags
--- PASS: TestRouter_RouterOptionsTagsApplied
--- PASS: TestRouter_MultipleMountsOnSameAgent
--- PASS: TestRouter_IssueExample
PASS

Note on go test ./... failures

The sdk/go/harness package has pre-existing failures on Windows that exist
on main before any of my changes. I verified this by running git stash (removing
my files entirely) and running go test ./... — identical failures appeared.

Root causes (none related to this PR):

• Tests expect Unix binaries (opencode, codex, gemini, claude-code) that
  are not installed in this environment
• Path separator mismatch: tests hardcode /tmp/... but Windows produces \tmp\...
• Tests expect executable files at temp paths that don't exist on Windows

All packages except harness pass cleanly:

ok   github.com/Agent-Field/agentfield/sdk/go/agent
ok   github.com/Agent-Field/agentfield/sdk/go/ai
ok   github.com/Agent-Field/agentfield/sdk/go/client
ok   github.com/Agent-Field/agentfield/sdk/go/did
ok   github.com/Agent-Field/agentfield/sdk/go/types
FAIL github.com/Agent-Field/agentfield/sdk/go/harness  ← pre-existing, not introduced by this PR

[CLAassistant]

All committers have signed the CLA.

[dhanadeep6]

Hi this is my first time doing this if there is any issues do tell me

[santoshkumarradha]

Hey @dhanadeep6, thank you, could you please click on the CLAassistant tag in the comment above and sign it? Once done we can proceed with the review :D

[dhanadeep6]

@santoshkumarradha done bro

[github-actions]

Performance

SDK	Memory	Δ	Latency	Δ	Tests	Status
Go	228 B	-19%	0.64 µs	-36%	✓	✓

✓ No regressions detected

[github-actions]

📊 Coverage gate

Thresholds from .coverage-gate.toml: per-surface ≥ 86%, aggregate ≥ 88%, max per-surface regression ≤ 1.0 pp, max aggregate regression ≤ 0.50 pp.

Surface	Current	Baseline	Δ
control-plane	87.40%	87.30%	↑ +0.10 pp	🟡
sdk-go	91.10%	90.70%	↑ +0.40 pp	🟢
sdk-python	93.63%	93.63%	↑ +0.00 pp	🟢
sdk-typescript	92.63%	92.56%	↑ +0.07 pp	🟢
web-ui	90.03%	90.01%	↑ +0.02 pp	🟢
aggregate	89.06%	89.01%	↑ +0.05 pp	🟡

✅ Gate passed

No surface regressed past the allowed threshold and the aggregate stayed above the floor.

[github-actions]

📐 Patch coverage gate

Threshold: 80% on lines this PR touches vs origin/main (from .coverage-gate.toml:thresholds.min_patch).

Surface	Touched lines	Patch coverage	Status
control-plane	0	—	➖ no changes
sdk-go	72	97.00%	✅
sdk-python	0	—	➖ no changes
sdk-typescript	0	—	➖ no changes
web-ui	0	—	➖ no changes

✅ Patch gate passed

Every surface whose lines were touched by this PR has patch coverage at or above the threshold.