Kane CLI should block execution immediately when the account has 0 credits

[MayurkPatil]

Summary

When a user with 0 credits runs kane-cli run with an objective, Kane CLI launches the TUI and attempts to interpret the objective before checking the credit balance. Because the LLM is unavailable at 0 credits, objective parsing fails, and the CLI incorrectly prompts the user for missing information (e.g., the target website) before finally surfacing the insufficient-credits error.

Credit validation should happen up front, so the command fails fast with a clear error and never launches the TUI or performs any LLM-dependent work.

Steps to Reproduce

1. Ensure the account has 0 credits.
2. Run:

   kane-cli run "go to amazon.in and search for TV under 25000 INR price constraint. Perform boundary value analysis using expand_bva on the budget threshold of 25000"
   

Actual Behavior

• Kane CLI launches the TUI and tries to interpret the objective.
• With 0 credits the LLM is unavailable, so objective parsing fails.
• The CLI cannot extract details such as amazon.in and prompts the user to provide the website.
• Only after the user supplies the website does the CLI display the insufficient-credits error.

Expected Behavior

Before launching the TUI or processing the objective, Kane CLI should validate the account's available credits.

If credits = 0, the command should terminate immediately with a clear message, e.g.:

You don't have enough credits to run this command. Please add credits to your account and try again.

At 0 credits, the CLI must not:

• Launch the TUI
• Attempt objective interpretation
• Ask follow-up questions
• Ask for the website
• Perform any LLM-dependent processing

Acceptance Criteria

• Credit balance is validated before objective processing begins.
• kane-cli run with 0 credits immediately shows an insufficient-credits error.
• The TUI is not launched when credits are 0.
• No objective parsing / LLM-dependent processing is attempted.
• No follow-up questions are presented to the user.
• Behavior is consistent across all kane-cli run objectives when the account has 0 credits.
• The error message clearly explains that additional credits are required to proceed.

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Suggested labels (could not be applied automatically — no triage access): bug, credit 0 case, error handling.

[MayurkPatil]

Labels to apply (couldn't be set at creation — no triage access on this repo):

• bug — this is a defect in the kane-cli run flow
• credit 0 case (new label) — tracks the zero-credits scenario
• error handling (new label) — pre-execution validation / clear error messaging

The two new labels don't exist in the repo yet. Could a maintainer create and apply them, or grant triage access so I can? Thanks!