Refactor config/logger structure for cohesion and consistent logging APIs

[Copilot]

✨ Enhancement

This PR addresses the refactoring opportunities identified by semantic function clustering: tracing validation was split from tracing config, several nano-files added navigation overhead, and logger helper APIs used inconsistent naming conventions. The result is tighter feature locality and a more uniform logging surface.

• Tracing validation co-located with tracing config

  • Moved validateOpenTelemetryConfig (and its trace/span ID regex helpers) from internal/config/validation.go to internal/config/config_tracing.go.
  • Keeps TracingConfig and its validation logic in one feature-focused file.

• Nano-file consolidation

  • Inlined guard policy env var constants into internal/config/guard_policy_parse.go and removed internal/config/guard_policy_env.go.
  • Moved payload-related defaults and registration into internal/config/config_core.go and removed internal/config/config_payload.go.
  • Moved SessionSuffix into internal/logger/common.go and removed internal/logger/session_helpers.go.

• Logger API naming standardization

  • Introduced canonical helper names:
    • Log*ToMarkdown
    • Log*ToServer
  • Updated call sites to use canonical names.
  • Kept Log*Md and Log*WithServer wrappers for compatibility to avoid breaking existing external usage.

Implementation approach:

// Canonical names
logger.LogInfoToMarkdown("startup", "Gateway started")
logger.LogWarnToServer("github", "backend", "Connection timeout")

// Compatibility wrappers remain valid
logger.LogInfoMd("startup", "Gateway started")
logger.LogWarnWithServer("github", "backend", "Connection timeout")

[Copilot]

Pull request overview

This PR refactors configuration and logger code to improve feature cohesion (tracing validation co-located with tracing config), reduce “nano-file” fragmentation, and standardize logger helper naming across the codebase while preserving backward compatibility.

Changes:

• Standardized logging helpers to canonical Log*ToMarkdown and Log*ToServer APIs and updated call sites/tests/docs accordingly (legacy Log*Md / Log*WithServer wrappers retained).
• Consolidated configuration code by relocating tracing validation into config_tracing.go, inlining guard-policy env var constants, and moving payload defaults/registration into config_core.go.
• Removed now-redundant nano-files (config_payload.go, guard_policy_env.go, session_helpers.go) after inlining/moving their contents.

Show a summary per file

File	Description
internal/server/tool_registry.go	Updates per-server logging calls to Log*ToServer during tool registration.
internal/server/http_helpers.go	Switches request rejection logging to LogErrorToMarkdown.
internal/server/guard_init.go	Updates DIFC/guard initialization logs to Log*ToServer.
internal/server/difc_log.go	Updates DIFC filtered-item logging to LogInfoToServer.
internal/mcp/errors.go	Standardizes backend connection error logging to Log*ToMarkdown / Log*ToServer.
internal/mcp/connection.go	Updates stderr/unified connection logs to canonical logger helpers.
internal/logger/startup.go	Moves startup helper to use LogInfoToMarkdown.
internal/logger/session_helpers.go	Removes file after moving SessionSuffix into common.go.
internal/logger/server_file_logger.go	Introduces Log*ToServer exports and keeps Log*WithServer wrappers for compatibility.
internal/logger/server_file_logger_test.go	Updates tests to use Log*ToServer.
internal/logger/README.md	Updates per-server logging examples to Log*ToServer.
internal/logger/markdown_logger.go	Introduces Log*ToMarkdown exports and keeps Log*Md wrappers for compatibility.
internal/logger/markdown_logger_test.go	Updates tests to use Log*ToMarkdown.
internal/logger/log_level_wrappers_test.go	Updates wrapper-coverage test mappings to new canonical names.
internal/logger/helper_functions_test.go	Updates helper-function tests to use canonical names.
internal/logger/doc.go	Updates package docs to list the canonical markdown/server helper APIs.
internal/logger/common.go	Updates logger API docs; adds SessionSuffix implementation here.
internal/launcher/log_helpers.go	Updates launcher logging to Log*ToServer while retaining session suffix usage.
internal/launcher/launcher.go	Updates launcher server logging to canonical Log*ToServer.
internal/config/validation.go	Removes tracing regex/validation implementation from validation module (moved).
internal/config/guard_policy_parse.go	Inlines guard-policy env var constants into this file.
internal/config/guard_policy_env.go	Removes file after inlining env var constants elsewhere.
internal/config/config_tracing.go	Adds regex helpers + validateOpenTelemetryConfig alongside tracing config.
internal/config/config_payload.go	Removes file after moving payload defaults/registration into config_core.go.
internal/config/config_core.go	Adds payload/log-related defaults/constants and registers payload defaults here.
internal/cmd/root.go	Updates startup/shutdown logging to Log*ToMarkdown.
AGENTS.md	Updates per-server logging example to LogInfoToServer.

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• Files reviewed: 27/27 changed files
• Comments generated: 2