feat(cli): move sessions, prompts and observations between projects

[ciltocruz]

🔍 Problem Description

Engram sometimes stores information in the wrong project and there is no way to move a session, prompt or individual observation that already has a project assigned to another project, neither via CLI, MCP nor TUI.

Verified today on v2.2.1:

• engram projects rescue-ownership --project <name> --session/--observation/--prompt <id> only rescues rows with NULL/empty project and reports already-owned rows as Blocked.
• engram doctor repair --project P --check ... --apply (from feat(doctor): detect and repair project-contaminated sessions #286) only reclassifies contaminated sessions when there is trustworthy evidence (git_remote/git_root or manual-save-{known-project} name), with SQLite backup under <ENGRAM_DATA_DIR>/backups/.
• MCP mem_update exposes no project field and the store rejects project changes with ErrObservationProjectImmutable (internal/store/store.go).
• engram projects consolidate and MCP mem_merge_projects {from,to} (admin profile) only merge name variants equivalent under normalization and reject arbitrary pairs like acmeapi → acme-api.
• engram projects merge --from/--to requested in feat(cli): merge two explicitly named projects when "projects consolidate --all" finds no groups #1296 does not exist in v2.2.1 and its building block (feat(store): explicit by-name project merge entry and record counts #1451, MergeProjectsByName + CountProjectRecords) is still OPEN.

💡 Proposed Solution

New engram move --to <project> [--session <id>]... [--observation <id>]... [--prompt <id>]... [--dry-run|--apply], reusing the transaction/journaling of RescueNullProjectOwnership but WITHOUT requiring empty project, with prior backup like doctor --apply, recalculated ownership_mode, and rejection when an observation would be split from its session (same anti-split guard as rescue).

MCP counterpart mem_move_records under admin profile with identical parameters.

In parallel, engram projects merge --from A --to B --dry-run|--apply on top of #1451.

📦 Affected Area

CLI (commands, flags)

🔄 Alternatives Considered

Evaluated existing paths, none of which move already-owned records: rescue-ownership (NULL/empty rows only), doctor repair (evidence-based reclassification only), projects consolidate / mem_merge_projects (normalization-equivalent name variants only), mem_update (project immutable by design).

📎 Additional Context

References:

• feat(doctor): detect and repair project-contaminated sessions #286 (closest existing, CLI/MCP repair with backup)
• bug: projects consolidate reports 'Merged: 0' without merging + mem_update does not persist project rename #179 (mem_update never persisted project change)
• feat(cli): merge two explicitly named projects when "projects consolidate --all" finds no groups #1296 (merge --from/--to, CLOSED without the subcommand)
• feat(store): explicit by-name project merge entry and record counts #1451 (OPEN, pending seam)
• Engram TUI permitir borrar sessions manualmente #94 (TUI delete sessions, delete not move)
• feat(sync): selective project export with interactive TUI #107 (selective export TUI, not move)

Acceptance criteria:

• Move one already-assigned session to another project via CLI with dry-run first and backup on apply.
• Move one already-assigned observation to another project via CLI with dry-run first and backup on apply.
• Move one already-assigned prompt to another project via CLI with dry-run first and backup on apply.
• MCP admin equivalent (mem_move_records).
• Docs updated.
• Existing rescue-ownership and doctor behavior unchanged.