python + typescript + bash: mirror the durability fixes from go/

Parity pass on the other three language templates. Same guarantees as
go/: survive server restart, client restart, half-open TCP, and long
outages; rejoin and drain prime-side backlog on reconnect, without
the user writing any of this in process.*.

python/main.py:
- grpc.keepalive_time_ms=10000, keepalive_timeout_ms=3000,
  keepalive_permit_without_calls=1 on the channel. Half-open TCP is
  detected within ~13s instead of the OS default ~2h.
- Exponential backoff with jitter; max_backoff_seconds config ceiling
  (default 120). Attempts counter resets after a session runs
  healthy for 60s so transient restarts don't escalate the delay.
- chain_id added as a required config field and sent as the
  x-chain-id gRPC metadata header (prime rejects streams without it).

typescript/src/main.ts:
- Same keepalive options on the @grpc/grpc-js client.
- Same exponential backoff + jitter logic.
- chain_id added to Config + metadata.

bash/:
- Config + README updated. The bash template uses Python's main.py
  as its runtime, so the behavioural changes above flow through
  without a separate main per language.

Docs: each README gains a "Durability guarantees" section so contract
authors see the invariants without reading the runtime code.

typescript/config.yaml

@@ -4,6 +4,11 @@
 # The gRPC server address to connect to
 server_address: "localhost:50051"
 
+# The public chain id on which this smart contract is registered.
+# Sent as the x-chain-id gRPC metadata header — prime rejects streams
+# without it.
+chain_id: "your-chain-public-id"
+
 # Your smart contract ID (provided by Dragonchain)
 smart_contract_id: "your-smart-contract-id"
 
@@ -19,6 +24,12 @@ use_tls: false
 # Number of concurrent workers for processing transactions
 num_workers: 10
 
-# Reconnect settings
-reconnect_delay_seconds: 5
+# Reconnect settings. The client uses exponential backoff with jitter:
+# effective delay = min(max_backoff_seconds, reconnect_delay_seconds * 2^attempts) + random(0, reconnect_delay_seconds).
+# Keep max_reconnect_attempts at 0 (infinite) unless you have a specific
+# reason to stop — the client is designed to survive arbitrarily long
+# outages and resume processing from the prime-side queue when the
+# server returns.
+reconnect_delay_seconds: 3
+max_backoff_seconds: 120
 max_reconnect_attempts: 0  # 0 = infinite retries