ref(cli): Drop unused installedAt timestamp from install manifest

[thecodedrift]

Remove the installedAt timestamp from the install manifest. It was written into .taskless/taskless.json on every install but never read by anything, so it only produced spurious diffs in committed manifests (surfaced while dogfooding via pnpm build:self — see #42).

What

• Drop installedAt from InstallState, the manifest type, the read path, and the write path.
• Retire the injectable now option on applyInstallPlan — the timestamp was its only consumer, so manifest writes are now fully deterministic.
• Schema migration v3 (0003-drop-installed-at.ts) strips the field from existing manifests; idempotent, and forward-migrates cleanly from every prior version.
• Tests updated: fixtures/assertions dropped the field, a migration test now asserts v3 strips installedAt while preserving other install fields, the version matrix covers a v3 start, and the two fresh-install version assertions bump 2→3.

Why

installedAt had no readers — confirmed by tracing every reference (all writes/pass-through). Removing it eliminates the per-run churn the manifest produced on re-install/dogfood.

Scope

This addresses the timestamp specifically (per-run churn). A real install still rewrites cliVersion/target-modes when those actually change — that's the broader "separate stable config from volatile install metadata" question in #42, intentionally left out here. The repo's own committed taskless.json is not hand-migrated; it upgrades lazily on next install.

Review notes

• Non-breaking → patch changeset. Existing manifests migrate automatically (v2 → v3).
• A v3 manifest read by an older CLI is tolerated (its migration runner sees version >= max and no-ops).

Refs #42

[Copilot]

Pull request overview

Removes the unused installedAt timestamp from the Taskless CLI install manifest so installs stop producing noisy, non-deterministic diffs in .taskless/taskless.json, and adds a schema migration to strip the field from existing manifests.

Changes:

• Remove installedAt from the install-state types and from the manifest read/write paths; drop the now injection from applyInstallPlan to make manifest writes deterministic.
• Add schema migration v3 (0003-drop-installed-at) to delete install.installedAt from existing manifests.
• Update CLI tests and migration/version expectations to reflect schema v3 and the removed field.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/cli/src/install/install.ts	Removes now option and stops writing installedAt into the next install state.
packages/cli/src/install/state.ts	Removes installedAt from InstallState and from manifest serialization/deserialization.
packages/cli/src/filesystem/migrate.ts	Drops installedAt from manifest type and registers migration v3.
packages/cli/src/filesystem/migrations/0003-drop-installed-at.ts	New migration that strips install.installedAt from existing manifests.
packages/cli/src/wizard/index.ts	Stops including installedAt in the wizard’s computed “next state” for diffs.
packages/cli/test/migrate-install.test.ts	Updates migration tests for v3 and asserts installedAt is removed while other fields persist.
packages/cli/test/onboard.test.ts	Updates expected schema version and removes installedAt assertions/fixtures.
packages/cli/test/init-no-interactive.test.ts	Updates expected manifest schema version to v3.
packages/cli/test/install-state.test.ts	Removes installedAt from round-trip install-state fixtures.
packages/cli/test/apply-install-plan.test.ts	Removes installedAt from install-state fixtures used by apply tests.
packages/cli/test/wizard-integration.test.ts	Removes installedAt from seeded install state fixture.
.changeset/drop-installed-at.md	Patch changeset documenting the removal and determinism improvement.

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