Fix agent-gen output location: route templates to af source tree

[stempeck]

Problem

When agent-gen or agent-gen-all.sh runs from a target project (e.g., ~/af/myproject/), it writes all artifacts — including Go role templates (.md.tmpl) — relative to the factory root. Templates need to be in the af source tree's internal/templates/roles/ directory for Go's //go:embed to compile them into the binary. Users must manually mv/cp files before running make build. This is too many steps for newcomers.

Goal

After running agent-gen, the only step a user needs is quickstart.sh — no manual file moves.

Design

Full design document and PR: #3

Design artifacts in .designs/af-5836e28c/:

• [design-doc.md] — Synthesized design with implementation plan
• [api.md] — API & interface design
• [data.md] — Data model analysis
• [ux.md] — User experience analysis
• [security.md] — Security analysis
• [integration.md] — Integration analysis
• [scale.md] — Scalability analysis
• [constraints.md] — Constraint definitions
• [constraint-audit.md] — Constraint verification
• [conflicts.md] — Conflict matrix
• [dependencies.md] — Dependency graph
• [problem-summary.md] — Problem analysis

Implementation Plan (from design-doc.md)

Phase 1: Source Root Resolution (Small)

• New file internal/config/source_root.go with ResolveSourceRoot(), isAgentFactorySourceTree(), SetBuildSourceRoot()
• Unit tests in internal/config/source_root_test.go
• One-line addition to cmd/af/main.go

Phase 2: Formula.go Integration (Small)

• Update runFormulaAgentGen() to route templates to source root
• Update runFormulaAgentGenDelete() for cleanup
• Update output messages and existing tests

Phase 3: Script Updates (Trivial)

• Add export AF_SOURCE_ROOT="$AF_SRC" to agent-gen-all.sh
• Verify quickstart.sh already handles it (it does)

Acceptance Criteria

• ResolveSourceRoot() returns factory root when it contains agentfactory go.mod
• ResolveSourceRoot() returns AF_SOURCE_ROOT when factory root is not source tree
• ResolveSourceRoot() returns error when neither is available
• All resolution paths validated with go.mod check
• Templates written to source root's internal/templates/roles/
• Workspace artifacts written to factory root's .agentfactory/agents/
• Source root resolution happens AFTER -o early return
• --delete removes template from source root
• agent-gen-all.sh sets AF_SOURCE_ROOT before calling agent-gen
• quickstart.sh continues to work unchanged
• make test passes

References

• Design PR: Fix agent-gen output location: route templates to af source tree #3
• Assignment bead: af-5836e28c
• Formula instance: af-f5411874

[stempeck]

Example github issue testing a one-shot end-to-end workflow after providing the manager this guidance:
#3 (comment)