fix(#75): clarify port-open error popup and correct config paths

[mixc6763-prog]

Summary

Three related fixes triggered by user reports on #75 — the "端口打开失败 / Ports Open Fail" popup is misleading users (and us) into chasing port-occupation problems, the diagnostic paths we ask reporters to inspect are out of date, and the generator path that produces .enhanced_config.yaml could silently emit a config without a usable HTTP-style port.

Commit 1 — docs(#75): use .config/clashfx for config and core log paths

The app moved from ~/.config/clash to ~/.config/clashfx long ago (see Paths.swift), but the READMEs and issue template still pointed users to the legacy directory. Reporters tail an empty file and we lose a debugging round-trip.

• 5 READMEs (en, zh-CN, zh-TW, ja, ru): correct $HOME/.config/clash → $HOME/.config/clashfx
• bug_report.md: add two diagnostic fields used during issue triage —
  • ~/.config/clashfx/.mihomo_core.log (only requested when Enhanced Mode is on)
  • grep of mixed-port / port / socks-port / external-controller from .enhanced_config.yaml (only requested when the user hits "Ports Open Fail")
• Drive-by: rename remaining ClashX template labels to ClashFX

Commit 2 — fix(#75): clarify port-open error popup with core log tail

ClashStatusTool.checkPortConfig shows the alert when mihomo_core's /configs API returns mixed-port = port = 0. That state is not a port-binding conflict — it usually means the generated .enhanced_config.yaml is missing port fields. The previous copy ("Ports Open Fail, Please try to restart ClashFX") sent users (and the issue #75 reporter) hunting for lsof collisions that don't exist.

Changes to ClashStatusTool.swift:

• Rewritten alert body describes the actual state (mixed-port = port = 0 / missing port fields) instead of implying a port conflict
• Appends the last 12 lines of ~/.config/clashfx/.mihomo_core.log to the alert when readable, so the real cause (TUN setup error, config parse error, etc.) is visible without digging through docs
• "Edit Config" now opens .enhanced_config.yaml when it exists, so the zero ports are visible directly; falls back to the original config.yaml when Enhanced Mode is off
• Two small private helpers (activeConfigPath, tailOfMihomoLog) keep the read-side concerns out of the alert flow

5 Localizable.strings updated (en/zh-Hans/zh-Hant/ja/ru): drop the misleading "Ports Open Fail, Please try to restart ClashFX" key, add the two new strings.

Commit 3 — fix(#75): always promote a usable mixed-port in Enhanced Mode config

The root cause of the popup itself. The previous fallback in clashWriteEnhancedConfig only injected mixed-port=7890 when all three of mixed-port, port, socks-port were zero. A source config with only socks-port (or only port in some edge cases) was passed through with mixed-port=0, and mihomo cannot synthesise a mixed-port default itself (RawConfig.MixedPort has no default tag). Result: .enhanced_config.yaml lacks a mixed-port, the GUI's usedHttpPort check returns 0, and the misleading alert fires.

Strategy mirrors ClashX.Meta's parseDefaultConfigThenStart (see main.go parseDefaultConfigThenStart):

1. Keep existing mixed-port if > 0
2. Otherwise promote the configured port or socks-port into mixed-port and drop the source field so mihomo doesn't try to bind the same number twice
3. Fall back to mixed-port=7890 only when nothing is configured

Type-assertion coercion is also hardened against int64 / uint64 / float64 / string scalars that subscription providers occasionally emit in place of bare ints.

• port_fallback.go: pure-Go helpers, no CGO so tests run on plain go test
• port_fallback_test.go: 23 cases covering coercion (incl. string, int64, uint64) and every promotion / fallback / conflict-cleanup branch

Verification

• xcodebuild -workspace ClashFX.xcworkspace -scheme ClashFX -configuration Debug (commit 1+2) → BUILD SUCCEEDED on clean derived data
• swiftc -parse on ClashStatusTool.swift → ok
• go test ./ in ClashFX/goClash/ → PASS (23/23)
• Cross-arch sanity (commit 3): GOOS=darwin GOARCH=arm64 and GOOS=darwin GOARCH=amd64 go build -buildmode=c-archive both succeeded
• Old key "Ports Open Fail..." no longer present in any Localizable.strings (grep confirmed)
• New key pair present in all 5 locale files

Note: goClash.a / mihomo_core binaries are in .gitignore and will be rebuilt by the release pipeline; nothing in this PR carries a checked-in binary diff.

Closes #75.