{channels, docs}: implement tenant-scoped Telegram long polling adapter

[XnLemon]

Fixes #31

Outcome

Implements a tenant-scoped Telegram long-polling Channel Adapter while preserving the existing trusted Binding and Gateway boundaries.

Docs-first delivery

• Documentation contract was published first in commit 4a3cd13.
• Runtime implementation landed in 47f6039; coverage/lint and review-closure commits are 81f5f1f, 54fe7dd, 850d4e1, and 5b35e1a.
• The implementation status is recorded in README.md and docs/docs/telegram.md.

Scope delivered

• Pins github.com/go-telegram/bot at v1.23.0.
• Adds trpcservice/channels/telegram with injectable Bot factory/client, runtime-only token handling, optional HTTPS API origin/HTTP client/poll timeout, worker count, redacted error hook, blocking Run(ctx), and Close.
• Accepts exactly one trusted active Telegram RoutingTarget; verifies getMe bot identity against canonical provider_account_id before handling updates.
• Maps ordinary private/group/supergroup text updates through gateway.NewChannelPrincipal, InboundMessage.Normalize, and the existing gateway.DispatchService.
• Uses Binding-aware stable external/request IDs and the existing process-local gateway.IdempotencyStore; pending duplicates do not dispatch and completed duplicates replay cached redacted events.
• Drains the complete Dispatch event stream, aggregates one logical text reply, splits at 4096 Unicode code points, preserves forum thread IDs, and uses a fixed redacted failure reply.
• Rejects edited/channel/callback/inline/command/service/media/non-text/malformed updates without dispatch; webhook, rich media, persistent outbox/idempotency, and cross-node ownership remain out of scope.
• Preserves caller cancellation during in-flight getMe and does not emit a misleading initialization hook for shutdown/deadline cancellation.
• Adds fake Bot/Factory and Gateway tests covering identity, isolation, mapping, event draining, Unicode chunking, duplicate delivery, commands, unsupported updates, redaction, getMe cancellation, polling hooks, and lifecycle.

Validation

• go test ./... -count=1
• go test -race ./... -count=1
• go vet ./...
• go build ./...
• python -m mkdocs build --strict -f docs\mkdocs.yml
• bash ./scripts/lint.sh
• gofmt changed Telegram files
• git diff --check
• Remote CI: Format & Lint, Build/Test/Coverage, MkDocs, and Codecov patch all pass on final head 5b35e1a.

Local Telegram package coverage is 90.8%; Codecov patch coverage is above the repository's 85% gate.
lint.sh skipped golangci-lint locally because it is not installed; the remote Format & Lint check passed.

Review notes

• Docs-stage review: LGTM on 4a3cd13.
• Final implementation review: two valid findings were fixed in 5b35e1a, then the fresh exact-head review found no remaining issues and posted fallback LGTM.
• The branch preserves unrelated pre-existing untracked workspace files. No merge is requested by this PR.

[codecov]

Codecov Report

❌ Patch coverage is 88.56383% with 43 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
trpcservice/channels/telegram/telegram.go	88.56%	27 Missing and 16 partials ⚠️

📢 Thoughts on this report? Let us know!

[XnLemon]

LGTM

[XnLemon]

LGTM