tlon-skill: Migrate the full posts command family to the pure command runner

[patosullivan]

Summary

This finishes moving the tlon posts command family off the legacy import-side-effect module and onto the injectable run(args, deps) command contract. posts react already used the contract; this change migrates the remaining subcommands — unreact, delete, edit — plus the family shell (bare posts, posts --help, unknown subcommands, and the unsupported send/reply guidance). With the whole family on the contract, the legacy scripts/posts.ts module is deleted and scripts/main.ts routes the entire posts family through the runner with no process.argv mutation.

User-facing behavior is unchanged: help text, usage errors, unsupported-command messages, success strings, and the post-id formatting pipeline are all preserved byte-for-byte. The win is testability and the removal of an auto-running command module.

What changed

• scripts/commands/posts.ts — grew from the react-only slice into the full family runner. Parsing produces a discriminated result covering help, react, unreact, delete, and edit; bare/unknown invocations throw a usage error and unsupported send/reply throw a command error, all before authentication. The id helpers (extractNumericId/formatUd) stay self-contained, and the existing-post lookup (around-cursor query, exact-id match, null-on-error) lives here where it is directly testable. The module imports only pure helpers (markdownToStory from ./story); the command-contract guard continues to pass.
• scripts/posts-runtime.ts — the process-backed facade gained removeReaction, deletePost, editPost, and a thin getChannelPosts lookup, plus now() (clock) and readFile() deps for edit. API failures are wrapped in commandError exactly as the react path already did.
• scripts/main.ts — the posts case now calls runPostsCommand(scriptArgs, createPostsDeps()) for every subcommand; the react-only special case, the process.argv rewrite, and the import('./posts') branch are gone.
• scripts/posts.ts — deleted. Nothing imports it.
• scripts/cli-test-matrix.ts — added nested-help, missing-arg, auth-required, and unsupported-command cases for the newly migrated subcommands, and extended HOSTILE_HELP_COMMANDS with posts unreact, posts delete, and posts edit. These flow into both the source hermetic suite and the built-binary smoke automatically.

Decision log (legacy quirks: preserved vs. tightened)

Every decision below preserves legacy behavior; each is covered by tests.

• Help token after a subcommand prints that subcommand's help before validation/auth (family help for unknown subcommands). Covered in-process for every known subcommand and the unknown-subcommand case, and via the hostile-config matrix. A help token also short-circuits the unsupported send/reply errors (posts send --help prints family help): this follows from parse order (help is resolved before the unsupported-command branch), but that specific combination is not separately pinned by a test.
• Edit message help-literal. posts edit <ch> <id> --help treats --help as the edit message and reaches auth — it does not print help. Its near-twin posts edit <ch> <id> --title --help does print edit help, because the message slice ends at the first option flag and the literal check never fires. Both adjacent cases are pinned in-process and as built-binary matrix cases.
• Flag-value parsing is positional with no validation. --title --image url takes --image as the title value. Preserved and tested.
• Trailing args after the required positionals are ignored for unreact and delete (and the emoji for react). Preserved and tested.
• Auth runs before any filesystem read. Edit authenticates, then looks up the existing post, then reads the --content file — so a nonexistent --content file fails with Missing Urbit config in a no-config environment, never a filesystem error. Pinned with an injected call-order assertion in-process and an auth-required case through the real binary.
• --content read/parse failures are caught after auth and the existing-post lookup and rethrown as a stable Error: <message> (exit 1, no stack/code frame). Both missing-file and invalid-JSON cases are tested.
• Payload shapes preserved. unreact calls removeReaction with postAuthor set to the current user; delete calls deletePost with the formatted id and current user id; edit merges metadata (new --title/--image override, existing title/image/description/cover preserved, null lookup → undefined) and stamps sentAt from the injected clock.
• Success strings unchanged: ✓ Reaction added, ✓ Reaction removed, ✓ Post edited, ✓ Post deleted.

Testing

• pnpm --filter '@tloncorp/tlon-skill' check (typecheck + unit + hermetic + built-binary smoke from a fresh build) passes.
• pnpm -r tsc passes for tlon-skill.
• In-process tests cover help/shell, per-subcommand missing-arg matrices, dotted/undotted/~ship/ ids, exact success strings, payload shapes, edit metadata merge (found / null / overrides / failed lookup), content via message vs. --content file, message-slicing edges, content read/parse failures, the injected clock, the help-literal quirk, positional flag-value parsing, and expected-vs-unexpected error propagation.
• Source and built CLI matrices cover nested help, missing-arg usage, auth-required valid invocations, the minimal edit help-literal, the auth-before-filesystem ordering, and the exact unsupported send/reply errors.

[linear-code]

TLON-5771