remove the ghost export command

[nahiyankhan]

Category: improvement
User Impact: The ghost export command is removed; move a Ghost package by copying its .ghost/ directory.
Problem: ghost export produced a standalone archive with a versioned schema (ghost.export/v1) that nothing reads: no import command, no registry, no in-repo or sibling consumer. It presented standalone distribution as a supported workflow while the real transport is the repo itself, and it carried a hand-rolled tar writer and a write-only metadata contract.
Solution: Remove the command, its archive format, and the private tarball module outright rather than deprecate. The package still travels with the repo or as a copied directory addressed with --package <dir>; docs and the skill bundle now describe that path. The locator audit was intentionally not migrated into validate; it can return when a real distribution workflow exists.

Validation:

• pnpm build: pass
• pnpm test: 209 passed (18 files)
• pnpm check: pass (biome, typecheck, packed-package, terminology, release tarball/workflows, vessel-light)
• Built CLI: no export in --help, --help --all, or ghost manifest
• Remnant sweep for ghost export, ghost.export/v1, export.yml, tarball symbols: zero active hits (historical CHANGELOG entries retained)

Changeset: added (minor, per the preview policy that breaking changes ship in minors)

ghost Review: not run because this repo has no root .ghost/ package; the change removes CLI surface only.

File changes

packages/ghost/src/commands/export-command.ts
Deleted: the entire export command (archive creation, export.yml stamping, locator audit, --strict).

packages/ghost/src/scan/tarball.ts
Deleted: private dependency-free tar/gzip writer; export was its only consumer.

packages/ghost/src/cli.ts
Drop registerExportCommand import and registration.

packages/ghost/src/commands/command-discovery.ts
Remove the export discovery entry from help and the manifest command.

packages/ghost/test/cli.test.ts
Remove export expectations from help/manifest tests; delete the five export tests; rewrite the portability round-trip to cp a .ghost/ directory and drive validate/gather/pull with --package outside a git repo (behavior preserved without the archive); delete tar helpers and the gunzipSync import.

packages/ghost/test/tarball.test.ts
Deleted with the tarball writer.

README.md
Drop ghost export from the command list; rewrite "The Package Travels" around copying the .ghost/ directory.

packages/ghost/README.md
Drop ghost export from the command list.

CLAUDE.md
Remove the ghost export row from the command table (covers the AGENTS.md symlink).

docs/purposes.md
Remove the future Fleet row that named exports as its input.

packages/ghost/src/skill-bundle/SKILL.md
Drop export from the loop; "Receiving a ghost package" now starts from a copied directory.

packages/ghost/src/skill-bundle/references/schema.md
Remove the export command-behavior bullet.

packages/ghost/src/skill-bundle/references/materials.md
Bundling rationale now reads "travel with a copied package" instead of "travel through export".

.changeset/remove-ghost-export.md
Minor changeset naming the removal.

Screenshots/Demos: N/A