The problem with fleet actions are that the harder SF we go, the closer to submarine battles and picket lines we get.
A starship is awfully hard to find in general. We have a celestially miniscule object that observers need to perform no small amount of searching for.
Thermographic searches are still line of sight based, and relatively short ranged.
Energy emissions are subject to a farraday cage type effect, and high-frequency lasers need to be interrupted to be detected.
I disagree that space combat will be long-ranged for any significant length of time. With the difficulty of detecting a ship, conflicts will be swift and brutal, based on speed and the amount of firepower delivered downrange more than defensive capabilities.
An attacking flotilla should be unconscionably numerous. With the advent of Inertial dampners, A fighter could be little more than a powerplant, thrust, control module, and a few weapon systems. Combat could be designed to take advantage of developments in dirtside hulls. Even if they're immune to projectiles, the energy has to go somewhere, throwing ships off attack vectors harmlessly. think of the invaders in ID4 and how severe impact just threw them off course, and thus all their weapons. Additionally, an attacking flotilla would need to rely on stealth for their approach - oblique orbital angles and high relativistic velocities.
Range in 0g vacuums becomes almost irrelevant. How much atmospheric bloom does a particle stream really suffer in in space? An object in motion is subject to very predictable forces. Range becomes dictated by the maneuverability of the target.
Plan a Planetary bombardment months in advance: slip into a system, calculate the rotation of a planet along its orbit, and deploy a cluster of individual projectiles at the same velocity in the opposite direction of planetary orbit - they'll smash into each other
Defense then becomes layers of early warning rather than direct interdiction. Large composite arrays become desirable in larger numbers and significant distances while under active surveilance. Planetary approaches need to be seeded with high velocity clouds of intervention....like counter-orbit debris fields.