docs(readme): move Install up and mention the import read-back of created items

[ryanlewis]

Two README changes, docs only.

• Install moved up. ## Install now comes right after the intro (demo, feature list, agents note), before ## CLI. A reader no longer has to scroll past about 800 lines of command reference to find it. The section's text is unchanged.
• Created-item read-back in the import section. The import section only covered the read-back of status changes. A short new "Reading back created items" subsection says that every to-do and project an import creates is read back (fix(import): read back the items an import creates #355): one line or JSON object per item, import partially applied when one never appears, search before re-running, and --no-verify skips it. It links to Logbook and import for the full rules.

Checked by reading the rendered diff. /code-review was skipped because the change is docs only.

Follow-up (not in this PR): the import section still says the CLI "forwards [the payload] verbatim", but when values are now rewritten as add sends them (today@6pm → YYYY-MM-DD@18:00). I left that wording to the --when work.