fix(mcp): Validate negative durations in search_traces (#8856)

[ParthKadam11]

Which problem is this PR solving?

• Resolves [Bug]: search_traces MCP tool does not validate against negative time durations #8856

Description of the changes

• Added validation for negative duration_min values in search_traces — returns "invalid duration_min: duration cannot be negative" instead of silently accepting it
• Added validation for negative duration_max values in search_traces — returns "invalid duration_max: duration cannot be negative" instead of silently accepting it
• Validations run immediately after time.ParseDuration succeeds, before any other duration comparisons

How was this change tested?

• Added TestSearchTracesHandler_Handle_DurationValidation — a table-driven test with 8 cases:
• Negative duration_min only, negative duration_max only, both negative
• Valid ranges, zero durations, duration_max < duration_min (existing check still works)
• Single-sided inputs (only min or only max provided)
• All 8 cases pass; ran make lint test successfully

Checklist

• I have read https://github.com/jaegertracing/jaeger/blob/main/CONTRIBUTING_GUIDELINES.md
• I have signed all commits
• I have added unit tests for the new functionality
• I have run lint and test steps successfully

AI Usage in this PR

• Light: AI provided minor assistance (formatting, simple suggestions)

[Copilot]

Pull request overview

This PR addresses #8856 by adding explicit validation to the search_traces MCP handler so negative duration_min / duration_max inputs are rejected immediately, preventing “impossible” duration filters from reaching the storage query layer.

Changes:

• Reject negative duration_min values with invalid duration_min: duration cannot be negative after successful parsing.
• Reject negative duration_max values with invalid duration_max: duration cannot be negative after successful parsing.
• Add a table-driven unit test covering negative durations, valid ranges, single-sided inputs, zero durations, and the existing duration_max < duration_min check.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
cmd/jaeger/internal/extension/jaegerquery/internal/mcptools/internal/handlers/search_traces.go	Adds fail-fast validation for negative parsed durations before comparing min/max or executing queries.
cmd/jaeger/internal/extension/jaegerquery/internal/mcptools/internal/handlers/search_traces_test.go	Adds a table-driven test exercising negative duration validation and confirming existing duration ordering validation still triggers.

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