chore: rename project to OpenCode-GraphAgent

[LeXwDeX]

Summary

Prepares the repository for going public under the new name OpenCode-GraphAgent.

docs: README rewrite

• Rewrote README.md / README.zh.md against the actual state of dev: removed stale claims (DAG "not compilable on dag-branch", 6-table schema, sub-DAG nesting, Goal auto-loop & removed slash commands, upstream install commands), documented the DAG engine as it is (workflow tool surface, scheduling/replan semantics, state machine + CQRS projection, crash recovery, deep admission & review lifecycle, TUI inspector/sidebar, 8 HTTP routes, dag.jsonc tiers)
• Added a "Why a DAG" section covering the four design premises (tiered orchestration, admission before graph construction, verdict disposal contract, evidence-based recovery)
• All names/links updated to LeXwDeX/OpenCode-GraphAgent

License hygiene

• Added NOTICE with explicit MIT/AGPL file boundaries (previously referenced but missing)
• Added AGPL-3.0 license text at packages/core/src/dag/LICENSE and packages/opencode/src/dag/LICENSE (previously dead links in README)

chore: Go module rename

• config_assistant module path github.com/opencode-dag/config_assistant -> github.com/LeXwDeX/OpenCode-GraphAgent/config_assistant (go.mod + 14 imports across 11 files)
• Verified: go build ./... and go test ./... pass, no stale references

Test plan

• Docs-only + Go submodule change; TS surface untouched. Typecheck gate applies.