fix(healthcheck): guard missing port delimiter in _parse_host_port

[vaibhavsrv]

Why this matters

In ods/scripts/healthcheck.py, _parse_host_port() parses TCP host and port targets. When called directly with a target missing a colon delimiter (such as "localhost" or "127.0.0.1" without port, or strings with untrimmed whitespace), raw.rsplit(":", 1) unpacks into a single element, raising an unhandled ValueError: not enough values to unpack (expected 2, got 1) rather than a descriptive domain error.

This change strips surrounding whitespace and explicitly asserts ":" in raw before splitting, raising ValueError("missing port delimiter ':' in target") if no port delimiter is present. Valid hostname and IPv6 bracketed targets remain untouched.

Validation

• Baseline reproduction: Calling _parse_host_port("localhost") raised unhandled unpacking ValueError: not enough values to unpack (expected 2, got 1).
• Post-fix verification: Running ods/tests/test_healthcheck_host_port_delimiter.py verifies that targets without a colon raise ValueError("missing port delimiter ':' in target"), and targets with surrounding whitespace are cleanly trimmed and parsed.
• Telemetry: Healthcheck test suite passes: test_healthcheck_host_port_delimiter.py passes cleanly (exit code 0). Wired into Linux CI workflow under healthcheck tests.

Overlap check

• fix(healthcheck): support bracketed IPv6 targets and strip brackets before TCP connect #5875 (merged today): Added bracketed IPv6 support to healthcheck.py. This change hardens host:port delimiter presence before splitting.
• fix(healthcheck): strip whitespace in parse_target and validate host #5950, fix(healthcheck): guard negative or zero timeout in check_tcp and check_http #5951, fix(healthcheck): enforce http and https url scheme in check_http #6078: Touched whitespace in _parse_target, timeout bounds, and HTTP scheme checking. This PR operates strictly on _parse_host_port.
• Does not modify TCP connect logic or retry loop contracts.

Risk / AI disclosure

AI-assisted investigation, implementation, and test regressions. This improves input validation and error clarity for target parsing. Independent human review and platform/runtime qualification remain gates. No running configuration, deployment or upstream merge changed.

Follow-up integration evidence

Composed with #5875, #5950, #5951, #6076, #6077, and #6078 at HEAD without conflicts. Production and test diffs passed together; healthcheck IPv6 and redirect policy suites remain intact.
Backlog composition was local-only (production/test diffs, excluding workflow/Makefile wiring); it is not an upstream merge or independent human approval. Declared live-review gates remain open.

[Lightheartdevs]

Thanks for this contribution. public-beta was promoted into main on 2026-09-24 and no longer receives changes, so we're closing pull requests that target it. This isn't a judgment on the change itself. If it's still needed, please rebase onto main and open a focused PR. See #7253 for details and the contribution policy.