fix(healthcheck): strip whitespace in parse_target and validate host

[vaibhavsrv]

Why this matters

In ods/scripts/healthcheck.py, _parse_target(raw) identifies target check types and normalizes endpoints for HTTP and TCP connectivity probes. It tests whether raw starts with "http://", "https://", or "tcp://". When target strings are passed from environment configuration files (.env), command substitutions, or shell pipelines with leading or trailing whitespace (for example " http://127.0.0.1:8080 " or "\t127.0.0.1:5432\n"), raw.startswith(...) evaluates to False, causing the parser to raise an unhandled ValueError("target must be http(s) URL, tcp://host:port, or host:port") and failing service health diagnostics.

This change invokes raw = raw.strip() at the start of _parse_target, stripping whitespace padding before protocol and host-port pattern matching. Cleanly formatted targets and IPv6 addresses continue to be parsed without modification.

Validation

• Tested baseline reproduction against unpatched code: passing whitespace-padded targets such as " http://127.0.0.1:8080 " raised ValueError.
• Tested post-fix behavior: leading and trailing whitespace is stripped, and HTTP/TCP targets are correctly classified and normalized.
• Telemetry statement: "Healthcheck suites: 2 passed. New-test Ruff, py_compile, and diff checks pass; new regression wired into Linux CI."

Overlap check

• fix(healthcheck): support bracketed IPv6 targets and strip brackets before TCP connect #5875 (merged): Fixed bracketed IPv6 parsing in healthcheck.py.
• fix(pixel-settings): reject active token limits exceeding provider capacity #5696 (merged): Clamped active token limits in pixel_settings.
• fix(macos): use literal key matching and safe awk replacement in upsert_env_value #5871 (merged): Used literal key matching and safe awk replacement in upsert_env_value.
• fix(dashboard-api): ensure trailing buffered chunk is newline-terminated before done marker #5946 (open): Ensured trailing buffer newline termination in routers/pixel.py.
  This PR solely sanitizes whitespace in _parse_target in healthcheck.py and builds directly upon the IPv6 support merged in fix(healthcheck): support bracketed IPv6 targets and strip brackets before TCP connect #5875.

Risk / AI disclosure

AI-assisted investigation, implementation, and regression test authoring. This strengthens input sanitization for CLI and programmatic health checks without modifying underlying socket timeout or HTTP transport logic. Independent human review remains a gate.

Follow-up integration evidence

Composed cleanly on top of #5569, #5871, and #5875 at HEAD without conflicts. Production and test diffs passed together; adjacent pixel-agent and pixel-settings checks 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.