Fix module path, remove x/exp, and fix AsyncBufferTime ticker

[tempurai]

Motivation

• Ensure the repository and import paths use the correct public URL github.com/tempurai/co across modules and docs.
• Prevent AsyncBufferTime from stalling and leaking goroutines by guaranteeing buffered batches are emitted on time boundaries and the ticker is stopped when the source ends.
• Remove dependency on golang.org/x/exp to avoid proxy/fetch issues and provide a local Ordered constraint.
• Modernize module metadata (Go version) and README guidance for fetching the module without a proxy.

Description

• Updated module path in go.mod and benchmark/go.mod, adjusted replace in benchmark/go.mod, and replaced imports across the codebase from the old path to github.com/tempurai/co.
• Replaced golang.org/x/exp usage by adding a local Ordered type in utils.go and using the standard slices package where appropriate.
• Fixed AsyncBufferTimeSequence in async_buffer_time_sequence.go by adding tickerStop, tickerStopOnce, a ticker goroutine that broadcasts on interval boundaries, and a stopTicker call when the source completes to avoid stalled goroutines.
• Updated README.md to point to https://pkg.go.dev/github.com/tempurai/co, added GOPROXY=direct example, and bumped go version to 1.22 in module files.

Testing

• No automated tests were executed in this environment for this change.
• Further verification should be performed by running GOPROXY=direct GOSUMDB=off go mod tidy and go test ./... in CI or a network-enabled local environment.

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Codex Task