Open / resume any past session in any profile (cross-profile session port)

[nitin-1926]

Summary

Let any past Claude Code session be opened/resumed in any profile, not just the profile it was created in. Today, resume only works inside the originating profile because each profile has an isolated config dir and claude --resume <id> only sees that profile's transcripts under the current cwd.

Use case: a conversation started in the personal profile should be resumable in work (different account, skills, MCPs, billing) without losing the history.

Mechanism

"Open session X in profile B" = port the transcript, then resume:

1. Copy the session file <profileA>/projects/<encoded-cwd>/<session>.jsonl into <profileB>/projects/<encoded-cwd>/ (same encoded-cwd subpath). Copy, not move — the original stays in profile A (fork semantics, non-destructive).
2. Launch claude --resume <session-id> in profile B, in the original cwd.
3. The conversation continues under profile B's account, skills, MCP servers, and billing.

Do not symlink — both profiles would append to one file and corrupt it. Copy = a clean fork.

Acceptance criteria

• Spike first: verify a hand-ported transcript is actually resumable under another profile via claude --resume <id>. Confirm whether Claude Code also requires the session to appear in that profile's ~/.claude.json history or validates the recorded cwd — if so, replicate that too. Do not build UI until this is proven.
• From the History browser (History: transcript reader + full-text search #4), "Open in profile…" action lets you pick a target profile.
• Porting copies (never moves) the transcript into the target profile under the same encoded-cwd.
• Resume launches in an embedded terminal (Embedded terminal (v1) #8) in the correct profile + original cwd.
• Handles: target profile already has a session with that id (skip/dedupe), missing cwd, unknown profile — all without crashing.
• Optional CLI counterpart, e.g. ccpm session port <id> --from <A> --to <B> (nice-to-have, decide during impl).

Dependencies

• History: transcript reader + full-text search #4 — History: session browser (to pick a session)
• Embedded terminal (v1) #8 — Embedded terminal v1 (to launch the resume)
• Resume session from History #10 — Resume session from History (this extends same-profile resume to cross-profile)

Risks / open questions

• Claude Code may index sessions outside the raw .jsonl (config history) — covered by the spike.
• Cross-account continuation: the ported conversation will be billed to and shaped by the target profile. That's the intended behavior, but call it out in the UI so it isn't surprising.