chore: simplify, modernize (Go 1.26), update deps

[rustatian]

Applied fixes

R (Reliability)

• writer.go: Add Unwrap() http.ResponseWriter so Hijacker, HTTP/2, and WebSocket promotion works through the metrics wrapper (was silently breaking those protocols)
• writer.go: Default code to 200 inside Write() — handlers that write a body without calling WriteHeader now record status 200 instead of -1

S (Simplification)

• plugin.go: *CounterVec with no labels replaced with prometheus.Counter for noFreeWorkers and uptime — cleaner API, no spurious With(nil) calls
• plugin.go: Size-1 buffered stopCh replaced with unbuffered channel + close() idiom — the correct Go pattern for a one-shot stop signal
• plugin.go: strconv.Itoa(rrWriter.code) captured once into statusCode; was evaluated twice (requestCounter + requestDuration)

M (Modernization)

• plugin.go: var otelVal/tp zero-decls reordered to group related declarations before the if ok block — minor scope clarity improvement

Deps

• go get -u all && go mod tidy

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 9eac792a-3f7c-4ab3-a665-5889c73325df

📥 Commits

Reviewing files that changed from the base of the PR and between e4da73d and fe78e25.

⛔ Files ignored due to path filters (1)

• go.sum is excluded by !**/*.sum

📒 Files selected for processing (2)

• plugin.go
• writer.go

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch chore/cleanup-modernize-deps

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[Copilot]

Pull request overview

Small reliability/cleanup pass on the http_metrics plugin: it makes the metrics ResponseWriter wrapper transparent to middleware that probes for http.Hijacker/HTTP/2 extensions, fixes the status label for handlers that only call Write, and simplifies a few internal patterns (label-less Counters, unbuffered stop channel via close, status string computed once). Also bumps OpenTelemetry contrib deps.

Changes:

• writer.go: add Unwrap() to expose the inner http.ResponseWriter, and default code to 200 inside Write() when WriteHeader was not called.
• plugin.go: replace label-less *CounterVec with Counter for noFreeWorkers/uptime, switch stopCh to unbuffered + close() in Stop, hoist strconv.Itoa(rrWriter.code) into a single statusCode, and minor declaration reorder.
• go.sum: drop old entries for otelhttp v0.68.0 and jaeger v1.43.0, keep the upgraded v0.69.0/v1.44.0 lines.

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated no comments.

File	Description
writer.go	Add Unwrap() for http.ResponseController and default status to 200 in Write().
plugin.go	Use scalar Counters, simplify stop signaling with close(), cache status string.
go.sum	Remove stale OTel contrib otelhttp/jaeger checksums superseded by the upgrade.

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