refactor: rename cc-session inject subcommand to inherit

[Mapleeeeeeeeeee]

Summary

• Renames the CLI subcommand cc-session inject to cc-session inherit. inject keeps working as a deprecated alias — it prints a one-line deprecation notice to stderr and forwards to the same handler — so existing scripts/skills using inject don't break during the transition.
• Updates the formatter's cc-session call-collapsing logic (parseCCSessionCommand / collapseCCSessionTools) to recognize inherit as well, while still correctly collapsing legacy transcripts that recorded cc-session inject (kept saying "injected" for those, "inherited" for new ones).
• Scope is CLI-layer + formatter only, by design: the internal/inject package and its exported API (State, LoadState, SaveState, SplitPages, RenderFullOutput, WritePage), and the benchmark package's InjectPages/CumulativeCostBWithInjectPages, were intentionally left unchanged — that's a separate future cleanup.
• README.md, SKILL.md, and docs/adr-001-collapse-cc-session-calls.md updated to describe inherit as the primary command, noting inject still works as legacy.

Test plan

• go build ./..., go vet ./..., go test ./... all pass
• Manually verified: cc-session (no args) help lists inherit, not inject
• Manually verified: cc-session inject <id> prints deprecation warning to stderr and behaves identically to cc-session inherit <id>
• Independently re-verified via a separate Codex review pass (build/test/behavior all confirmed)
• Added/updated formatter tests covering both legacy inject and new inherit transcript collapsing

🤖 Generated with Claude Code

https://claude.ai/code/session_01GypgpBVuZDFuxAWoqVxxeL