[Bug] `gitt issues register` cannot encode `register_issue` string arguments after #1335

[statxc]

Description

After #1335, gitt issues register no longer goes through ContractInstance.exec(...). It now routes through the new IssueCompetitionContractClient.register_issue(...) method, which calls _exec_contract_raw('register_issue', ...) → _encode_args('register_issue', ...).

That new path is broken before any extrinsic is submitted.

metadata.json declares register_issue with two str arguments:

• github_url
• repository_full_name

But IssueCompetitionContractClient._encode_args() only handles u32, u64, u128, AccountId, and array32. Anything else hits the fallback:

raise ValueError(f'Unsupported type: {type_def} for arg {arg_name}')

So every register_issue call fails while encoding github_url, before compose_call is ever invoked.

Affected Code

• gittensor/cli/issue_commands/mutations.py — issue_register() now calls client.register_issue(...) (introduced in Bump bittensor stack and drop substrate-interface #1335).
• gittensor/validator/issue_competitions/contract_client.py
  • register_issue() → _exec_contract_raw(method_name='register_issue', ...)
  • _exec_contract_raw() → _encode_args(...)
  • _encode_args() has no str branch.
• gittensor/validator/issue_competitions/metadata.json — register_issue declares github_url and repository_full_name as str.

Steps to Reproduce

No live chain required — the failure happens entirely inside local argument encoding.

Against current test at fc503f9:

from gittensor.validator.issue_competitions.contract_client import (
    IssueCompetitionContractClient,
)

# Bypass __init__ so we don't need a Subtensor connection.
client = IssueCompetitionContractClient.__new__(IssueCompetitionContractClient)

client._encode_args(
    "register_issue",
    {
        "github_url": "https://github.com/owner/repo/issues/1",
        "repository_full_name": "owner/repo",
        "issue_number": 1,
        "target_bounty": 10_000_000_000,
    },
)

Observed:

ValueError: Unsupported type: str for arg github_url

The full CLI path reaches the same encoder via:

gitt issues register
  → mutations.issue_register()
  → IssueCompetitionContractClient.register_issue(...)
  → _exec_contract_raw(method_name="register_issue", ...)
  → _encode_args("register_issue", ...)   # raises here

Expected Behavior

gitt issues register should encode the register_issue arguments and submit the contract call. Specifically, _encode_args should SCALE-encode str as compact-length-prefixed UTF-8 bytes (the SCALE encoding of Vec<u8>).

Actual Behavior

register_issue fails during local argument encoding, before any on-chain submission. The CLI can only surface a pre-submission error similar to:

register_issue error: Unsupported type: str for arg github_url

Impact

#1335 was intended to remove the local .contract artifact requirement for issue registration ("removes the runtime requirement to have smart-contracts/issues-v0/target/ink/issue_bounty_manager.contract built locally before registering an issue"). The replacement path achieves that goal but cannot register any issue, because register_issue always carries string arguments.

This breaks the owner-only gitt issues register workflow on current test.

#1335's own description notes that "Basic things were tested, but not the chain interaction itself" — this is the gap that comment was flagging.

Suggested Fix

Add SCALE string encoding to _encode_args() for type_def == "str":

• UTF-8-encode the value.
• Prepend the SCALE compact length of the byte string.
• Append the bytes.

The compact-length helper should cover at least modes 0 (n < 64), 1 (64 ≤ n < 16384), and 2 (16384 ≤ n < 2³⁰) so that longer repo names / URLs don't fail at the >64-byte boundary.

A regression test should cover register_issue specifically, e.g.:

• Construct the client via __new__ (no chain dependency).
• Call _encode_args("register_issue", {...}) with both a short URL and a URL long enough to push the encoded length past 64 bytes.
• Assert it does not raise.
• Assert the encoded bytes begin with the correct SCALE compact-length prefix followed by the UTF-8 bytes, in order, for github_url then repository_full_name, then u32 issue_number (4 bytes LE), then u128 target_bounty (16 bytes LE).
• Negative case: a non-str value for github_url raises a clear error.

Prior Art / Not a Duplicate

#987 / #988 (and the parallel #993) proposed removing the str fallback as dead code, with bodies explicitly stating:

"str appears only in register_issue (never routed here)… register_issue is never called through _exec_contract_raw → _encode_args — it is called from the CLI (mutations.py) via a different execution path."

That premise was true at the time, and those PRs were closed without merging.

#1335 inverted that premise: register_issue is now routed through _exec_contract_raw() → _encode_args(), making the previously unreachable str path reachable in production — and now broken, because the str branch was never implemented.