refactor!: replace REPL with one-shot execution

[tisonkun]

Summary

• remove the interactive REPL and require an explicit CLI subcommand
• preserve the familiar scopeql run <STATEMENT> positional input and -f/--file <FILE> script input
• read redirected stdin when neither statement text nor a file is provided
• keep stdin selection implicit instead of adding --command or -f - aliases
• best-effort cancel the active server-side statement when scopeql run receives Ctrl+C
• delete REPL-only terminal code and remove the reedline and indicatif dependency trees
• document the new one-shot workflow and breaking changes

Motivation

ScopeQL statements are submitted independently and the current REPL does not provide server-side session semantics. Maintaining terminal editing, history, highlighting, slash commands, and signal workarounds therefore adds a large stateful surface without changing execution semantics.

The revised run command keeps the existing inline statement and explicit file interfaces while adding a shell-native path for generated or multiline input. Redirected stdin avoids additional flags and lets the shell handle files, pipelines, and heredocs directly.

Dropping the local execution future does not stop a statement already accepted by ScopeDB. The one-shot path therefore retains the existing statement cancellation protocol and sends POST /v1/statements/{id}/cancel on interruption.

CLI shape

scopeql run "SHOW DATABASES;"
scopeql run -f queries.scopeql
scopeql run < queries.scopeql
scopeql run <<"SCOPEQL"
SHOW DATABASES;
SHOW SCHEMAS;
SCOPEQL

When stdin is a terminal, scopeql run without input fails immediately with a usage-oriented error. Running bare scopeql displays command help instead of opening a REPL. -f - has no special stdin behavior.

While a statement is active, the first Ctrl+C asks ScopeDB to cancel that statement, waits up to five seconds, skips all remaining statements, and exits with status 130. A second Ctrl+C stops waiting immediately. Cancellation failures and timeouts report the statement ID because server-side execution may still be running.

Breaking changes

• remove the REPL and all slash commands
• make bare scopeql display help instead of opening an interactive session
• stop prompting for first-connection setup from a bare invocation; scopeql connection add remains explicit

Validation

• cargo x lint
• cargo x check
• cargo x test --no-capture (41 tests passed)
• generated scopeql run --help smoke check
• real SIGINT smoke test against a local mock server, verifying the cancel endpoint, cancellation result, and exit status 130

Open question

This draft deliberately keeps the existing config.toml discovery and --config-file behavior. Automatically discovering a project-local scopeql.toml deserves a separate decision because it changes credential placement and trust semantics.

[tisonkun]

fyi @andylokandy @leiysky