docs: correct coverage figures, stale examples, and broken links

[jasoet]

Coverage figures

Stale in both directions, and three packages had none. Regenerated from a real unit+integration run (-tags=integration, Docker-backed testcontainers):

package	README said	actual
server	77.1%	97.0%
grpc	71.2%	82.0%
ssh	78.2%	85.6%
db	76.7%	83.5%
concurrent	95.1%	100.0%
otel	84.8%	89.5%
compress	82.4%	85.3%
temporal	81.2%	84.5%
docker	83.1%	84.1%
config	97.6%	96.4%
rest	92.9%	93.0%
argo	missing	94.8%
retry	missing	100.0%
base32	missing	100.0%

The README also told readers to open output/coverage-all.html — no task produces that file — and described a methodology that did not match the task it named. Now: figures come from task test:integration → output/coverage-integration.html; task test:complete additionally runs argo (needs k8s) → output/coverage-complete.html.

examples/otel was entirely pre-v3

/v2 import path, struct-literal configs throughout, and a link to otel/examples/example.go — a directory that does not exist.

The example program itself used &otel.Config{...}. That still compiles, but loggerProviderSet is unexported, so a struct literal silently skips the default zerolog logger provider that NewConfig installs. The example was teaching a pattern that quietly loses logging. Converted to functional options; verified the program still prints its documented output (the no-op example needed an explicit WithoutLogging() to stay all-false, which is exactly the trap worth showing).

Broken links and unrunnable instructions

• docker/README.md linked the deleted logging package and said "OpenTelemetry v2".
• Three READMEs linked a CONTRIBUTING.md that was never written. Rather than delete the promise, wrote the file — the workflow it describes already existed, scattered across README and INSTRUCTION.
• examples/grpc/README.md linked ../README.md (nonexistent examples/README.md).
• examples/compress and examples/ssh gave run instructions from <pkg>/examples/ directories that do not exist, and omitted the example build tag — so they could not have worked. Both verified with go build -tags=example.

Full markdown link scan now clean except two links inside historical docs/plans/ records, deliberately left as point-in-time documents.

Backlog hygiene

Split resolved from open, each with a pointer to where the fix landed. Notably, two entries were verified still present rather than assumed fixed: ssh's accept-loop reads t.stopCh unlocked at three points while Start reassigns it under t.mu, and t.wg.Add after Accept still races Close's wg.Wait. Only the busy-spin half of that item was ever fixed. Recorded with line numbers; left open deliberately as a v3.x item.

Two backlog items are now closed as decisions rather than defects — docker's Inspect/GetStats escape hatches (ADR 0004) and the server/grpc lifecycle divergence (ADR 0005).

Verification

task ci:check green (0 lint issues), go vet -tags='example integration argo' ./... clean, CLAUDE.md == AGENTS.md parity confirmed.